explain xkcd - User contributions [en]

2567: Language Development

2022-01-14T01:55:56Z

198.41.238.107: /* Explanation */

{{comic
| number = 2567
| date = January 12, 2022
| title = Language Development
| image = language_development.png
| titletext = The worst is the Terrible Twos, when they're always throwing things and shrieking, "forsooth, to bed thou shalt not take me, cur!"
}}

==Explanation==
{{incomplete|Created by a AUTOMATON - What the baby hast sayeth? Forsooth change this scribbeth when editing this vellum. Do NOT delete this tag too soon.
[Nah, delete it. The use of archaic English for humorous purposes should be left to those actually conversant with archaic English. Never funny otherwise.]}}
[[Megan]] and [[Cueball]] are having what could appear to be a typical conversation about her child's ability to learn languages really fast. But the comic mixes up the concept of learning a language and the development of languages over time. The joke comes from the a conflation of two different things.

The conventional meaning of {{w|Language development}} is the process by which infants begin to talk, that is to understand and produce intelligible speech. The field of {{w|Language acquisition}} (sometimes called language development) seeks to understand how baby humans are able to rapidly comprehend, internalize, and begin producing a new language so rapidly.

Instead of starting with {{w|babbling}}, the first stage of normal language development, this baby's form of "language development" seems to be the linguistic form: going through all of the theoretical stages of the evolution of the English language, from Proto-Indo-European to Germanic to Old English.

In {{w|Comparative linguistics}} and {{w|Historical linguistics}}, {{w|Proto-Indo-European_language|Proto-Indo-European}} is a theorized common ancestor of the Indo-European language family. {{w|Proto-Germanic_language|Proto-Germanic}} is a reconstructed language formerly spoken in Iron Age Scandinavia. It developed out of Proto-Indo-European and is the proposed common ancestor for all {{w|Germanic languages}}. {{w|Old English}} would have developed out of Proto-Germanic. Modern English developed out of Old English with many additions from French (which comes from a different branch of the Indo-European language family). This parody of language development parallels the discredited {{w|theory of recapitulation}} in embryo development, sometimes expressed as "ontogeny recapitulates phylogeny", in which a developing animal embryo (ontogeny) was once thought to go through stages resembling successive adult stages in the evolution of the animal's remote ancestors (phylogeny).

In linguistics, reconstructed words from proto-languages are commonly marked with an asterisk (*) to show that the word forms are not attested by any historical sources but created as a proposed ancestor word. The baby says the Proto-Indo-European roots that the words "milk" and "please" are derived from. Obviously, the speakers of Proto-Indo-European did not speak in roots, but used words made from the roots, so the way the baby talks does not reflect any stage of development of the proto-language.

Some sounds babies make are hard to interpret.{{citation needed}} However, humans have a tendency to recognize known things and patterns. They see what they want to see and hear what they want to hear. Thus, a parent familiar with Proto-Indo-European may falsely hear their baby speak Proto-Indo-European by misinterpreting unintelligible sounds.

Perhaps this is an alternate universe where every baby has to gradually develop their language skills along a historical path rather than a child-developmental one, until they reach the ultimately developed modern language of their parents (in this case of Modern English).

There have been alleged {{w|language deprivation experiments}} where newborn infants were not exposed to any spoken language in order to find the "natural human language", in the days before ethics review boards would have forbidden such cruel treatments. Such experiments are known today to be a source for psychological problems at least. Alleged outcomes in the apocryphal sources range from the deprived children imitating other sounds in their environment, to them dying.

In the title text, Randall describes a 2 year old child as speaking in {{w|iambic pentameter}} and in Elizabethan English, a meter and dialect of modern English used by {{w|Shakespeare}} more than 400 years ago. The [https://www.verywellfamily.com/terrible-twos-and-your-toddler-2634394 Terrible Twos] are a colloquialism referring to the developmental tendency of two-year-olds to have more temperamental behavior, as the child's developing assertion of autonomy and self-identity clash with other expectations of behaviour, before hopefully acceptably balancing their assertiveness with social normatism.

==Transcript==
:[Megan and Cueball are looking to the left at a baby with dark hair. The baby sits on the left side of a table in an elevated baby chair.]
:Megan: He's only 1, so he still mostly speaks proto-Indo-European.
:Megan: But we've heard a few Germanic words already, so Old English can't be far off.
:Cueball: They progress so fast!
:Baby: *Melg-
:Baby: *Pl(e)hk-

{{comic discussion}}

[[Category:Language]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring babies]]

Talk:2566: Decorative Constants

2022-01-11T05:49:05Z

198.41.238.107:

I don't have any idea what to put in the actual description, but whoever does should probably note that r(in) - r(out) equals zero, not one. And multiplying by a constant 0 absolutely changes the value! [[User:GreatWyrmGold|GreatWyrmGold]] ([[User talk:GreatWyrmGold|talk]]) 21:59, 10 January 2022 (UTC)
: rout and rin are different values. The subscripts represent different instances of the same variable at different point. In the same way, you might calculate something happening over a time interval tend - tstart . [[Special:Contributions/172.69.71.77|172.69.71.77]] 23:02, 10 January 2022 (UTC)
::Yes for sure they are two different values. On the other hand if μ is not 1 then the it is not just decorative! D on the other hand is just a proportionality constant, which may have a value other than 1. I have tried to put something in the explanation here. Quite a bit. Do not really now anything about Drag, so just took it from the wiki page. Also I hope someone can explain the formula in the image, as I'm sure it is just something about the flow, that would relate it to a drag equation. --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 23:41, 10 January 2022 (UTC)

Note that the title text is pretty much word-for-word a repeat from Randall's book *How To*. In Chapter 11: *How to Play Football*, he misuses the drag equation, and mentions this fact in more depth, in a footnote. Bit of trivia! --[[Special:Contributions/162.158.134.79|162.158.134.79]] 23:13, 10 January 2022 (UTC)
:Nice, I will have to check up on that. Thanks. --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 23:41, 10 January 2022 (UTC)
:Can confirm this, the book mentions that the "traditional tribute to Euler and Bernoulli" comes from Frank White's ''Fluid Mechanics'' textbook. [[User:Clam|Clam]] ([[User talk:Clam|talk]]) 01:08, 11 January 2022 (UTC)
:: There it is, page 266 in the 1986 2nd edition: "They both have a factor ½ as a traditional tribute to Bernoulli and Euler, and both are based on the projected area..." https://books.google.com/books?id=wGweAQAAIAAJ&q=traditional -- [[Special:Contributions/172.70.162.5|172.70.162.5]] 02:13, 11 January 2022 (UTC)

of course, the c^2 im e=mc^2 is just as decorative, when using natural units where c=1.... [[Special:Contributions/172.68.50.171|172.68.50.171]] 00:29, 11 January 2022 (UTC)

: And the resulting equation is then just e=m - or m=e which is beautiful and profound. "Mass is Energy". Without the complications, you stop thinking of it as a PROCESS for converting one into the other and get the more profound point that Mass and Energy are the exact same thing. [[User:SteveBaker|SteveBaker]] ([[User talk:SteveBaker|talk]]) 03:33, 11 January 2022 (UTC)
==Count down clock==
;Keep discussion of comic above this, and further discussion of countdown here below!!!
Any idea what's going on with the clock that's counting downwards in the banner? Currently counting down from 20 days 16 hours? [[Special:Contributions/172.70.214.95|172.70.214.95]] 22:08, 10 January 2022 (UTC)
:(Simultaneous edit) What is the days-hours-minutes in the box above the comic referring to? The image itself is dated yesterday, as you can see by saving it. Worst-case-scenario, is this a countdown to the end of XKCD? [[Special:Contributions/108.162.245.223|108.162.245.223]] 22:11, 10 January 2022 (UTC)
:: It's going to hit zero at around midnight on Jan 31st 2022 CST? [[User:SteveBaker|SteveBaker]] ([[User talk:SteveBaker|talk]]) 22:16, 10 January 2022 (UTC)
:::'''Posted [[Talk:2565:_Latency#Countdown|this]] on the previous comics discussion. But lets take it here where there will be more traffic:''' --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 22:44, 10 January 2022 (UTC) -- Copy paste from previous comics discussion:
::::Damn you beat me to it ;-). But I have made a [[2565:_Latency#Trivia|Trivia]] here on this comics page and links to more detail on the [[xkcd Header text]] page. I believe you are a day of, but someone will likely correct me if I'm wrong. As I can see it will be January 31st, 9:59 in Randall's home town Boston.--[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 20:06, 10 January 2022 (UTC)
:::::But damned if I can wait. Sure millions will watch the page when it goes to zero! At least it is no April 1st. :-D --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 20:10, 10 January 2022 (UTC)
::::Yeah - you're right - I messed up. So as I type this, it's Jan 10th 2022 at 4pm - 1600 hrs Mountain time - which is 1800 hours EST. At this moment, the countdown reads 20d 16h 0m - so Jan 30th + (18+16) hours = which is Jan 30th + 34 hours - which is Jan 31st + 10am in Boston (EST). [[User:SteveBaker|SteveBaker]] ([[User talk:SteveBaker|talk]]) 23:05, 10 January 2022 (UTC)
:::::Hey great, can see they agree in the link to reddit below. So happy I got it right both in UTC and Boston. It will be 15:59 here in DK. Not 16:00. ;-) --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 23:44, 10 January 2022 (UTC)

Counting down to Backwards Day? --[[Special:Contributions/162.158.91.88|162.158.91.88]] 23:28, 10 January 2022 (UTC)
:There's a reddit thread discussing it: https://www.reddit.com/r/xkcd/comments/s0oynl/xkcd_countdown_timer_20d_21h_49m_remaining_until/ I think the most likely guess is that Randall has a new book coming out, although the time of day is weird for a book release. [[User:Barmar|Barmar]] ([[User talk:Barmar|talk]]) 23:40, 10 January 2022 (UTC)
::Would still seem strange if it came out that day with only promotion before being a count down. But then again, he will have the xkcd communities boiling if he gives no other hint. So every one will see if he promotes a book. Also as they wrote at the time I looked at reddit I do not think it is the end of xkcd, or Webb related. Although Webb was the first I thought about. But I mean even if it came to L2 at that day, it is not going to any specific point but just in orbit. --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 23:47, 10 January 2022 (UTC)

::The date fits the idea of it being Backwards Day (https://nationaldaycalendar.com/backward-day-january-31) but what about the choice of time? [[User:SteveBaker|SteveBaker]] ([[User talk:SteveBaker|talk]]) 03:38, 11 January 2022 (UTC)

Someone has noticed the image is changing with pixels added at the bottom left corner and is keeping track of it here: https://munvoseli.github.io/xkcd-countdown/ [[Special:Contributions/198.41.238.107|198.41.238.107]] 05:49, 11 January 2022 (UTC)

2564: Sunshield

2022-01-06T01:00:24Z

198.41.238.107: flash after shutter - what if it's a time exposure

{{comic
| number = 2564
| date = January 5, 2022
| title = Sunshield
| image = sunshield.png
| titletext = RIP the surface of Mars
}}

==Explanation==
{{incomplete|Created by THE BRILLIANCE OF THE JWST SCARRING THE FACE OF THIS WIKI- Please continue expanding and improving the explanation. Do NOT delete this tag too soon.}}
JWST stands for {{w|James Webb Space Telescope}}, a space telescope launched about 2 weeks prior to publication of the comic. It has a {{w|James Webb Space Telescope sunshield|sunshield}} to protect its instruments from the heat of the sun and to keep them below 40 K (-233 °C/-388 °F). Deployment of the sunshield was completed the day before the comic was published. The JWST has to undergo a complex sequence of deployment steps to unfold parts that had to be packed tightly for launch. This sequence has 344 possible points of failure that would render the very expensive space telescope useless; 75% of them led up to the successful full deployment of the sunshield. Thus successful steps are widely celebrated, with this comic an example of such a celebration.

Ordinary cameras use a {{w|Flash (photography)|flash}} to take pictures in low-light situations. Outer space is very dark{{Citation needed}}, so this comic posits that the JWST has a very powerful flash to compensate for this. Most astronomical cameras don't use flash photography -- they depend on the light either emitted by objects themselves (e.g., stars) or from nearby very bright objects (e.g., Solar System planets that reflect the Sun's light). A flash generally doesn't work for many reasons:
* It would take too long for the light of the flash to return to the telescope - at least twice the time that it had already taken for the original image to arrive on its own.
* The shutter in this comic operates (with a click) ''before'' the flash is emitted, so light from the flash wouldn't even reach the camera's {{w|photodetector}}. It is however possible that the camera is using a time exposure and that the shutter was still open when the flash occurred.
* Not enough 'flash' light would return due to it uselessly spreading in all directions. Instead, in a telescope mirrors and/or lenses focus the light, and long exposure times are used to collect enough of the current light to form a decent image.
* A flash powerful enough to overcome the previous difficulty would have to be inordinately powerful. This would raise significant questions about powering it, and would damage (or at least disturb) many of things the flash would still be able to illuminate.
* The objects and phenomena of interest of JWST are, by dint of their extreme distance, being seen as they were in the early stages of the universe, and emit light that potentially gives vital clues about that era, only marginally this side of the current visible-horizon of our apparently expanding universe. Should our flash ever reach them (assuming they still exist) and we have the patience to await the return (assuming ''we'' still exist), this will only reveal the much older versions of whatever they have become and only in the form of light that we have swamped them with.
* Before this, any intervening civilization that possesses (or can still develop) the necessary capabilities will have at the very least responded, if not retaliated, to the original flash. Their response might be far less humorous.

There are some examples of astronomical research done using things similar to a flash. {{w|Radar astronomy}} involves emitting radio waves (microwaves) that bounce off distant planets, asteroids, comets, etc., and analyzing the returned waves. The {{w|Lunar Laser Ranging experiment}} uses lasers, which are loosely related to flashes for photography, to measure the distance between Earth and Moon. The outward light is concentrated upon the approximate area of the lunar target, which employs an {{w|Retroreflector|optical trick}} to send most of that which actually struck it back to the approximate area of the source equipment.

The comic assigns the sunshield a new, comical purpose of shielding the Sun and Earth (which is roughly in the same direction as the Sun, due to the deployment at the {{w|Lagrange point|L2 Lagrange point}}) from this flash, rather than the other way around. When the camera is taking a picture, the comic shows a totally dark shadow behind the shield.

The comic also has the camera making a "click" sound. In traditional mechanical cameras, this sound comes from the {{w|Shutter (photography|shutter}} opening and closing, and digital cameras mimic this sound so the user (and subject, when human) knows when the picture is being taken. JWST won't actually click -- it doesn't have a shutter, as it takes long-exposure digital images, and [https://www.imdb.com/title/tt0078748/taglines in space no one can hear you click].

The telescope also tells the universe to smile for the picture. The universe doesn't have a mouth to smile with{{Citation needed}}, although there are a number of features on Solar System objects that look like faces; this is a phenomenon called {{w|pareidolia}}. The most well known is the {{w|Man in the Moon}}, but there are [https://www.universetoday.com/121551/faces-of-the-solar-system/ numerous others].

The title text suggests that, due to the sunshield not being angled to shield Mars, Mars's surface has been badly scarred by the flash. This implies ''incredible'' strength of the flash, perhaps to ensure the light can return from its destinations, comparable to {{tvtropes|KillSat|death-ray satellites}} in fiction.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}
:[The James Webb Space Telescope is floating through space, a black background.]
:JWST: Okay, universe-
:JWST: Smile!

:JWST: ''Click''

:[A bright flash glows from the telescope, turning most of the panel white. The left side is blocked and kept dark by the telescope's sunshield.]

:[Caption below the panel:]
:Astronomy fact: The purpose of the JWST sunshield is to protect the Sun and the Earth from the telescope's powerful flash.

{{comic discussion}}
[[Category:Space]]
[[Category:Telescopes]]

Talk:2467: Wikipedia Caltrops

2022-01-01T21:01:26Z

198.41.238.107:

seems more like flares (which distract) than caltrops (which physically impair) to me. [[Special:Contributions/162.158.222.122|162.158.222.122]] 16:31, 24 May 2021 (UTC)

I'd say "Well, I now know what I'm doing for the next few hours!", except that I suspect that this isn't even going to be the half of it... [[Special:Contributions/141.101.98.46|141.101.98.46]] 16:37, 24 May 2021 (UTC)
::👍 [[User:OhFFS|OhFFS]] ([[User talk:OhFFS|talk]]) 21:45, 24 May 2021 (UTC)

except 'caltrops' is a funnier word than 'flares' and we get the gist anyway. [[Special:Contributions/108.162.237.4|108.162.237.4]] 17:23, 24 May 2021 (UTC)

no WAY randall is a jon bois fan
[[Special:Contributions/173.245.52.175|173.245.52.175]] 17:38, 24 May 2021 (UTC)

Flares draw fire to prevent missiles from reaching their target. Caltrops impede the actual motion of the vehicle. If the links are as distracting as Randall implies, I think his choice makes sense!
[[Special:Contributions/108.162.215.92|108.162.215.92]] 00:34, 25 May 2021 (UTC)

Flares do " draw fire" but because they are more visible to heat seakeking missiles than engine jet engine heat. This seems like a solvable problem, missile and flare wise.[[Special:Contributions/162.158.75.202|162.158.75.202]] 03:44, 25 May 2021 (UTC)

Shouldn't the links be given as QR codes rather than plain text, which would have to be read and re-typed into a device with a suitable web browser? [[Special:Contributions/108.162.219.28|108.162.219.28]] 00:54, 25 May 2021 (UTC)
:Having to type the URL would be more distracting to driver of the car behind? And it's not like it is exactly easy to aim your phone camera to and read the QR code on a flying banner from the car in front of you, in addition to using smartphone mean traffic law violation. And text in URL also spoiler the link content a bit to invite interest. [[Special:Contributions/172.70.49.196|172.70.49.196]] 02:45, 25 May 2021 (UTC)
:QR codes for urls are more a marketing ploy. The usage for typing urls into a webbrowser can be as easily done by an OCR algorithm on the camera image. Sebastian --[[Special:Contributions/172.68.110.118|172.68.110.118]] 12:02, 25 May 2021 (UTC)
:Plain text (if it contains interesting words) will catch the driver's attention. QR codes are easy to ignore.

It looks like "List of Fictional Colors" [https://web.archive.org/web/20200720071214/https://en.wikipedia.org/wiki/List_of_fictional_colors used to exist] but was deleted [https://web.archive.org/web/20200731090020/https://en.wikipedia.org/wiki/List_of_fictional_colors late July 2020] [[Special:Contributions/172.69.33.119|172.69.33.119]] 04:11, 25 May 2021 (UTC)

I have nothing useful to add but wanted to point out that "as easily distracted as me." is grammatically incorrect - it should instead be "as easily distracted as I." [[Special:Contributions/172.70.100.54|172.70.100.54]] 13:25, 25 May 2021 (UTC)
:[https://www.explainxkcd.com/wiki/index.php/1576:_I_Could_Care_Less XKCD 1576] [[User:OhFFS|OhFFS]] ([[User talk:OhFFS|talk]]) 14:53, 26 May 2021 (UTC)
:Firstly, no native speaker of English says "as [whatever] as I". Secondly, the whole phrase, "someone as easily distracted as me." is governed by the preposition "by", not just "someone". See §8 of the article on "as" in H.G. Fowler's A Dictionary of Modern English Usage (1926) for case after "as". [[Special:Contributions/198.41.238.107|198.41.238.107]] 21:01, 1 January 2022 (UTC)

The wikipedia list should have a warning before it due to a HIGH nerd sniping potential. No doubt that was the intent. --Hman

It's a legitimate technique. I've been trying to read this explanation page for 48 hours but it keeps sending me down a Wikipedia hole that I have to dig myself out of. [[User:Xseo|Xseo]] ([[User talk:Xseo|talk]]) 10:14, 26 May 2021 (UTC)

Talk:2467: Wikipedia Caltrops

2022-01-01T21:00:54Z

198.41.238.107: "as me" is correct in this sentence, even by the old rules.

seems more like flares (which distract) than caltrops (which physically impair) to me. [[Special:Contributions/162.158.222.122|162.158.222.122]] 16:31, 24 May 2021 (UTC)

I'd say "Well, I now know what I'm doing for the next few hours!", except that I suspect that this isn't even going to be the half of it... [[Special:Contributions/141.101.98.46|141.101.98.46]] 16:37, 24 May 2021 (UTC)
::👍 [[User:OhFFS|OhFFS]] ([[User talk:OhFFS|talk]]) 21:45, 24 May 2021 (UTC)

except 'caltrops' is a funnier word than 'flares' and we get the gist anyway. [[Special:Contributions/108.162.237.4|108.162.237.4]] 17:23, 24 May 2021 (UTC)

no WAY randall is a jon bois fan
[[Special:Contributions/173.245.52.175|173.245.52.175]] 17:38, 24 May 2021 (UTC)

Flares draw fire to prevent missiles from reaching their target. Caltrops impede the actual motion of the vehicle. If the links are as distracting as Randall implies, I think his choice makes sense!
[[Special:Contributions/108.162.215.92|108.162.215.92]] 00:34, 25 May 2021 (UTC)

Flares do " draw fire" but because they are more visible to heat seakeking missiles than engine jet engine heat. This seems like a solvable problem, missile and flare wise.[[Special:Contributions/162.158.75.202|162.158.75.202]] 03:44, 25 May 2021 (UTC)

Shouldn't the links be given as QR codes rather than plain text, which would have to be read and re-typed into a device with a suitable web browser? [[Special:Contributions/108.162.219.28|108.162.219.28]] 00:54, 25 May 2021 (UTC)
:Having to type the URL would be more distracting to driver of the car behind? And it's not like it is exactly easy to aim your phone camera to and read the QR code on a flying banner from the car in front of you, in addition to using smartphone mean traffic law violation. And text in URL also spoiler the link content a bit to invite interest. [[Special:Contributions/172.70.49.196|172.70.49.196]] 02:45, 25 May 2021 (UTC)
:QR codes for urls are more a marketing ploy. The usage for typing urls into a webbrowser can be as easily done by an OCR algorithm on the camera image. Sebastian --[[Special:Contributions/172.68.110.118|172.68.110.118]] 12:02, 25 May 2021 (UTC)
:Plain text (if it contains interesting words) will catch the driver's attention. QR codes are easy to ignore.

It looks like "List of Fictional Colors" [https://web.archive.org/web/20200720071214/https://en.wikipedia.org/wiki/List_of_fictional_colors used to exist] but was deleted [https://web.archive.org/web/20200731090020/https://en.wikipedia.org/wiki/List_of_fictional_colors late July 2020] [[Special:Contributions/172.69.33.119|172.69.33.119]] 04:11, 25 May 2021 (UTC)

I have nothing useful to add but wanted to point out that "as easily distracted as me." is grammatically incorrect - it should instead be "as easily distracted as I." [[Special:Contributions/172.70.100.54|172.70.100.54]] 13:25, 25 May 2021 (UTC)
:[https://www.explainxkcd.com/wiki/index.php/1576:_I_Could_Care_Less XKCD 1576] [[User:OhFFS|OhFFS]] ([[User talk:OhFFS|talk]]) 14:53, 26 May 2021 (UTC)
:Firstly, no native speaker of English says "as [whatever] as I". Secondly, the whole phrase, "someone as easily distracted as me." is governed by the preposition "by", not just "someone". See §8 of the article on "as" in H.G. Fowler's A Dictionary of Modern English Usage (1926) for case after "as".

The wikipedia list should have a warning before it due to a HIGH nerd sniping potential. No doubt that was the intent. --Hman

It's a legitimate technique. I've been trying to read this explanation page for 48 hours but it keeps sending me down a Wikipedia hole that I have to dig myself out of. [[User:Xseo|Xseo]] ([[User talk:Xseo|talk]]) 10:14, 26 May 2021 (UTC)

Talk:2555: Notifications

2021-12-16T10:05:37Z

198.41.238.107:

I wrote that the time in the title text does not seem to have any special meaning, the only thing a quick google search gave me was the bible verse "Think not that I am come to send peace on earth: I came not to send peace, but a sword." which is irrelevant to the comic as far as I can tell. Is there something I missed? -- [[User:256 256.256.256|256.256.256.256]] ([[User talk:256 256.256.256|talk]]) 08:52, 16 December 2021 (UTC)

:I assume it has something to do with time zones, but not sure.[[Special:Contributions/162.158.222.123|162.158.222.123]] 09:40, 16 December 2021 (UTC)

Is it just a weird coincidence that today’s xkcd is also about how to stop a tedious conversation?

Talk:1137: RTL

2021-12-07T05:21:23Z

198.41.238.107:

There's a typo in the comic - hte should be eht for "the" spelled backwards -jars99

:Unless you consider "th" a single character, which by the way makes a lot of sense as it is derived from old-english "eth". {{unsigned|62.245.198.190}}
::Unless you further consider that "they" doesn't share that in the comic, making it internally inconsistent. [[Special:Contributions/76.122.5.96|76.122.5.96]] 11:40, 21 November 2012 (UTC)
:::It should be noted that at some point, "the" was corrected. [[User:Rawmustard|Rawmustard]] ([[User talk:Rawmustard|talk]]) 16:42, 22 November 2012 (UTC)

Acutally, unicode 202e doesn't "flip proceeding text back-to-front", it overrides the direction, setting it to "right-to-left" for the following text. It's back-to-front for most of us like "left-to-right" is to other writing systems. I know it's nitpicking, but xkcd readers should appreciate the symmetry. [[User:BKA|BKA]] ([[User talk:BKA|talk]]) 07:23, 21 November 2012 (UTC)

I don't see the reversed title. My window manager is not UTF-8 compatible, so when a window title is set to string containing UTF-8 characters, it doesn't change. This brings the question if it really is a browser problem or if the browsers behave as expected and the window manager is at fault. -- [[Special:Contributions/89.177.52.2|89.177.52.2]] 09:17, 21 November 2012 (UTC)

:It's not a ''problem'' per sec. Browsers that get the reversed title are processing the UTF symbol correctly, there's no bug there. And the window manager has no bearing on the title text except for maybe font. [[User:Davidy22|Davidy22]][[User talk:Davidy22|<tt>(talk)</tt>]] 09:32, 21 November 2012 (UTC)

::Well its the window manager that renders the window title, but it is composed by the Browser. I think that the browser should insert an appropriate number of U+202c characters, in this case it should be "xkcd: [U+202e]LTR[U+202c] - Mozilla Firefox". That would render as xkcd: RTL - Mozilla Firefox". By the way, the tab caption in Firefox is "xkcd: LTR". In Chromium and Opera it is shown correctly as "xkcd: RTL". [[User:Joha.ma|Joha.ma]] ([[User talk:Joha.ma|talk]]) 09:47, 21 November 2012 (UTC)

Another way to see this in effect is to try to type in this test page: http://www.fileformat.info/info/unicode/char/202e/browsertest.htm - and this also works in etherpad, as suggested in the caption.--[[User:Anarcat|Anarcat]] ([[User talk:Anarcat|talk]]) 00:09, 22 November 2012 (UTC)

Black Hat seems to have used U+202b, not e. The individual characters are left-to-right. Check the D, E, L, N, S, and ? [[Special:Contributions/24.193.153.138|24.193.153.138]] 02:46, 22 November 2012 (UTC)
:No, U+202e does not actually mirror the characters themselves, just the displayed order. U+202b only changes the order for characters that don't have embedded direction, such as the period, which can be used with multiple languages. [[User:Bugefun|Bugefun]] ([[User talk:Bugefun|talk]]) 05:00, 22 November 2012 (UTC)
::Actually, it does mirror some characters, namely those that have the ''mirrored'' property. For example, the parentheses or mathematical relations like the less-than sign. [http://www.unicode.org/Public/UNIDATA/BidiMirroring.txt Here] is a list of them. --[[User:Ulm|Ulm]] ([[User talk:Ulm|talk]]) 12:34, 22 November 2012 (UTC)
:::‮The text is not always mirrored - some browsers and font-sets do not 'understand' U+202E, so the text here might be displayed with a box before it. [[Special:Contributions/173.49.135.77|173.49.135.77]] 15:24, 27 December 2012 (UTC)

The title of this comic has an embedded RTL in the title, as has been noted somewhere. Because of this, Randall's Archive page is now screwed up, with all titles before this comic (listed after this comic on the Archive page in descending order) now being reversed. Ha, ha! He hacked himself!
[[Special:Contributions/70.111.5.179|70.111.5.179]] 01:59, 14 January 2013 (UTC)larK

just randomly came across this comic today, and not only is the title LTR, but also preceeded by some gibberish characters: "â€®LTR" using firefox, don't know how - i don't think it has always been like that on my machine... [[Special:Contributions/162.158.89.187|162.158.89.187]]
:Same here (as in on Firefox). Kinda messed up my 'looking stuff up on explainxkcd' workflow... It also shows up like that on InternetExplorer.[[Special:Contributions/108.162.229.110|108.162.229.110]] 15:21, 2 December 2019 (UTC)
::It's working for me right now; title shows as RTL, and Firefox's title bar shows "xkcd: xoferiF allizoM - RTL". As for those gibberish characters, that's U+202e in the wrong encoding -- probably Windows-1252 instead of UTF-8. Check your browser's encoding if it's still happening. --[[User:Aaron of Mpls|Aaron of Mpls]] ([[User talk:Aaron of Mpls|talk]]) 23:54, 16 June 2020 (UTC)
:::For me it is xkcd:emhorC eglooG - RTL --[[User:Lupo|Lupo]] ([[User talk:Lupo|talk]]) 05:28, 17 June 2020 (UTC)

I can't remember which key to hold down while doing the 202e bit. So far, Ctrl, left-Alt, right-Alt, and Ctrl-Alt don't work. [[Special:Contributions/198.41.238.107|198.41.238.107]] 05:21, 7 December 2021 (UTC)

2550: Webb

2021-12-04T07:15:44Z

198.41.238.107: /* Explanation */ put my comment about Cueball's question back in, with a longer explanation

{{comic
| number = 2550
| date = December 3, 2021
| title = Webb
| image = webb.png
| titletext = Each one contains a chocolate shaped like a famous spacecraft and, for the later numbers, a pamphlet on managing anxiety.
}}

==Explanation==
{{incomplete|Created by the JAMES WEBB SPACE TELESCOPE - Please change this comment when editing this page. Do NOT delete this tag too soon.}}
This comic depicts an {{w|advent calendar}} geared toward astronomers anticipating the launch of the {{w|James Webb Space Telescope}}.

The James Webb Space Telescope is (currently, but after [[2014: JWST Delays|many prior delays]]) scheduled to be launched on the 22nd of December. Christmas will indeed come early for astronomers should the launch be successful.

A normal advent calendar marks the days until Christmas by allowing 'doors' to be opened, or other means of revealing some treat/picture. This is often from the 1st of the month until the 'big reveal' on the 25th, though other schemes may exist for cultural reasons. This particular calendar features 18 hexagonal features, intended to be sequentially accessed over several days, deliberately similar to the 18 gold-beryllium mirrors designed to fold out to form the JWST's compound reflector. The Hubble Space Telescope's mirror panels, along with those on the the yet to launch James Webb Space Telescope, are hexagonal. The first door is on the 5th, two days after this comic's publication date, while the last is the 22nd, marking 'The Big Day'.

Cueball's question could be interpreted two ways: Cueball doesn't know about JWST, so he is asking why this advent calendar ends before Christmas; or Cueball does know about JWST and its history of delays, so he is asking why the calendar ends on 22 when there is no certainty in that launch date (and also implying that he expects it to be delayed).

The title text references the fact that chocolates in advent calendars are often molded into different shapes, and the fact that the later numbers have a "pamphlet on managing anxiety" is probably supposed to quell the impeding fear that the launch would be delayed. The telescope's launch was initially planned for 2007, but due to various redesigns, financial issues, accidents, flaws, and the {{w|COVID-19 pandemic}}, the launch date was pushed back to 2011, then 2013, 2018, 2020, May 2021, October 2021, and finally to the current launch date in December 2021. It may also allude to post-launch concerns; even if the launch goes well, there will still be nervousness about reaching its intended observation point, unfolding/deploying successfully, and passing its final calibrations without problems. There are effectively no means to rescue/repair this expensive piece of equipment should anything be discovered to be amiss, unlike the {{w|Hubble Space Telescope}}, which was visited a number of times by the Space Shuttles to remedy and enhance various features. (There exist issues with even the HST that cannot currently be considered repairable, without the Shuttles or any proven replacement, and the Webb is to be located far beyond Hubble's operational orbit.)

The JWST has been referenced previously in [[1730: Starshade]], [[2014: JWST Delays]], and [[2447: Hammer Incident]], as well as indirectly in [[975: Occulting Telescope]] and [[1461: Payloads]].

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}

:[Cueball and Ponytail are looking at an advent calendar. The advent calendar is in a hexagon shape, with 18 smaller hexagons with numbers ranging from 5-22 written on them.]
:Cueball: The hexagons are nice. But why does it end at 22?
:[Caption below the panel:]
:Astronomer Advent Calendar

{{comic discussion}}

2533: Slope Hypothesis Testing

2021-10-27T04:47:22Z

198.41.238.107: /* Explanation */ better method is to test additional students, rather than re-testing same three

{{comic
| number = 2533
| date = October 25, 2021
| title = Slope Hypothesis Testing
| image = slope_hypothesis_testing.png
| titletext = "What? I can't hear--" "What? I said, are you sure--" "CAN YOU PLEASE SPEAK--"
}}

==Explanation==
{{incomplete|Created by a SCREAMINGLY SIGNIFICANT STAT STUDENT. Note: there's a name for when the bone in your ear pulls away after exposure to loud noise, could be thematic to reference it. There's probably also a name for the statistical mistake the comic demonstrates. Do NOT delete this tag too soon.}}
"Slope hypothesis testing" is a method of testing the significance of a hypothesis involving a scatter plot.

In this comic, [[Cueball]] and [[Megan]] are performing a study comparing student exam grades to the volume of their screams. Student A has the worst grade and softest scream, but Student B has the ''best'' grades and Student C the ''loudest'' scream. A trendline has been plotted, indicating a positive correlation between grades and volume...but the p-value is extremely high, indicating little statistical significance to the trend. P-value is based on both how well the data fits the trendline and how many data points have been taken; the more data points and the better they fit, the lower the p-value and more significant the data.

Megan complains about the insignificance of their results, so Cueball suggests having each student scream into the microphone a few more times. (The three students are still there as they can be seen behind them. The three students look like schoolkids; one of them is [[Science Girl]].)

Having the students scream again will not help though, because it only provides more data on the screaming without providing more data on its relation to exam scores, and is a joke around poor statistical calculations likely made in the field today. The p-value is incorrectly recalculated based on the increased number of measurements without accounting for the fact that observations are nested within students. Each student has exactly the same test scores (probably referencing the same datum as before) and have vocal volume ranges that don't drift far either (each seems to have a range of scream that is fairly consistent and far from overlapping). Megan is pleased by these results, but Cueball belatedly realizes this technique may not be scientifically valid. Cueball is correct (presuming that they are using simple linear regression). A more appropriate technique would account for the non-independence of the data (that multiple data points come from each person). Examples of such techniques are multilevel modeling and Huber-White robust standard errors.

Measuring data multiple times can be a way to increase its accuracy, but does not increase the number of data points with regard to another metric, and the horizontally clustered points on the chart make this visually clear. A more effective and scientifically correct way of gathering data test would be to test other students and add their figures to the existing data, rather than repeatedly testing the same three students.

Common statistical formulae assume the data points are statistically independent, that is, that the test score and volume measurement from one point don't reveal anything about those of the other points. By measuring each individual's scream multiple times, Cueball and Megan violate the independence assumption (a person's scream volume is unlikely to be independent from one scream to the next) and invalidate their significance calculation. This is an example of pseudoreplication. Furthermore, Megan and Cueball fail to obtain new test scores for each student, which would further limit their statistical options.

In current AI, there's a push toward "few-shot learning", where only a few data items are used to form conclusions, rather than the usual millions of them. This comic displays danger associated with using such approaches without understanding them in depth.

Additionally, a common theme in some research is the discovery of correlations that do not survive independent reproduction. This is because randomness with too few samples produces apparent correlations, and Randall has repeatedly made comics about this hopeful error.

In the title text, Megan and Cueball are trying to yell over each other, asking each other to speak up so they can be heard, presumably because they are having trouble hearing from the yelling experiment. Or possibly they have trouble speaking audibly because they score poorly on statistics exams.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}
:[Three points are labeled "Student A", "Student B" and "Student C" from left to right in a scatter plot with axes labeled "Stats exam grade" (60-100) and "Scream loudness (decibels)" (86-94) with a trend line. Student B has the highest exam grade, followed by Student C and then Student A.]
:[A line goes from the trend line to a box containing the following:]
:β=1.94
:p=0.586

:[In a frameless panel, Megan reads a piece of paper while facing Cueball while three students look at them from the background.]
:Megan: Darn, not significant.
:Cueball: We need more data. Have them each try yelling into the mic a few more times.

:[The same scatter plot as in the first panel except with more points for each of the students with slightly different decibel values, and the text in the text box changed to:]
:β=1.94
:p=0.037*
:<nowiki>*</nowiki>Significant!

:[Similar panel to the second one]
:Megan: Perfect!
:Cueball: Are you ''sure'' we're doing slope hypothesis testing right?

{{comic discussion}}

[[Category:Comics featuring Megan]]
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Science Girl]] 
[[Category:Statistics]]
[[Category:Charts]]

2528: Flag Map Sabotage

2021-10-14T04:36:21Z

198.41.238.107: Initial explanation

{{comic
| number = 2528
| date = October 13, 2021
| title = Flag Map Sabotage
| image = flag_map_sabotage.png
| titletext = Delaware hopes to explore the western edge of areas marked with the Belgian flag, once the tornadoes die down.
}}

==Explanation==
{{incomplete|Created by a GOD-EMPEROR OF GREATER DELAWARE - Please change this comment when editing this page. Do NOT delete this tag too soon.}}

The comic refers to a style of map that uses the flags of countries to fill in the country. This flag contains a fake map legend that causes the colors to be reinterpreted according to the legend. For example the south of Russia would become part of Greater Delaware as the bottom of the Russian flag is red, which the legend marks as Greater Delaware. A number of common flag color are included.

The title text refers to the flag of Belgium, which consists of three vertical stripes in the order black, yellow red. The western part of Belgium would, according to the legend, be unexplored, while the eastern part would be Greater Delaware. The middle would therefore be a tornado zone separating the unexplored area from Greater Delaware. Depending on how the flags are aligned it would be possible to explore from the south. The north is not viable as rebel forces would be present.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}
:[A flag displays a white country-shaped area surrounded by a red field. Inside the shape sits a map legend.]

:Map Legend
:[Bright blue rectangle] Disputed territory
:[Green rectangle] Newly independent
:[Blue rectangle] Demilitarized zone
:[Yellow rectangle] Tornado warning
:[Dark blue rectangle] Held by rebel forces
:[Red rectangle] Greater Delaware
:[Black rectangle] Unexplored

:[Caption below panel]
:Our new country's flag sabotages those maps where geographic areas are colored in with flag patterns.

{{comic discussion}}

[[Category:Comics with color]]
[[Category:Maps]]
[[Category:Sabotage]]

2514: Lab Equipment

2021-09-17T22:39:37Z

198.41.238.107: /* Explanation */ Inserrt "citation needed" tag where one is obviously needed :)

{{comic
| number = 2514
| date = September 10, 2021
| title = Lab Equipment
| image = lab_equipment.png
| titletext = I've been working on chocolate bar annealing techniques to try to produce the perfect laser s'more. Maybe don't mention that on the grant application though.
}}

==Explanation==
{{incomplete|Created by a NEODYMIUM-DOPED MARSHMALLOW S'MORE- Please change this comment when editing this page. Do NOT delete this tag too soon.}}

This comic claims that in every science lab, there exists some piece of equipment that sticks around less for being useful, and more because the scientists and technicians just think the device is really cool.

The comic presents a laboratory containing equipment for analysis of substances. While giving [[Cueball]] a tour of the lab equipment, [[Ponytail]] shows a spectrometer — a device that examines light emitted from or passed through samples to fingerprint emission or absorption lines in the mix of light. Next she shows the "Nd:YAG" lasers. It is unknown if the multiple lasers are for redundancy or if they have different specifications and are for different tests. "Nd:YAG" stands for {{w|Nd:YAG_laser|neodymium-doped yttrium aluminum garnet}}; it is a lasing medium commonly used in lasers. Lastly she shows off a decommissioned laser not used in experiments, but rather for toasting marshmallows.

The claim that such things are almost universal is, in fact, very realistic. When doing any research, especially cutting-edge research, it's often difficult to predict what equipment will be useful or not, so it's inevitable those some things will be purchased, and not turn out to be very effective in their experiments. Some of these things will end up being sold, put into storage, repurposed, or even thrown away, but some equipment is enjoyed by the researchers, despite a lack of official uses, and so will end up being kept around. Researchers, being human, are going to do some things in the lab for their own amusement, rather than because it's part of a formal experiment, and if equipment has already been purchased, keeping it because it's enjoyable is usually overlooked. Additionally, just playing around with high-end equipment can occasionally lead to useful discoveries. Basic research is difficult to plan out, and sometimes just letting scientists play around with powerful equipment can produce unexpected results, which can lead to new scientific understanding.

The title-text mentions that she's using "annealing techniques" to make the perfect s'more. A {{w|s'more}} is a popular treat in the United States and Canada, consisting of one or more toasted marshmallows and a layer of chocolate sandwiched between two pieces of graham cracker. {{w|Annealing (materials science)|Annealing}} is more commonly a heat-treatment technique used to influence the nature of the crystals in metals for structural reasons. This is done when jewelry is molded from molten metal, but more likely Randall means a use of annealing in scientific research. Annealing is also used in {{w|Annealing_(glass)|glass production}}. This suggests that Ponytail is trying to use lasers and/or other specialized heating equipment to control the melting process of the chocolate, in conjuction with precision toasted marshmallows, to perfect this treat. She points out that this shouldn't be mentioned on the grant application. When labs apply for grants to purchase or upgrade equipment, or to fund research projects, they emphasize the scientific principles that could be advanced (and potential useful products that might be produced) as a result of their research. The idea that researchers might be using the equipment to amuse themselves and work on whimsical side projects would be unlikely to impress the groups offering the grant,{{citation needed}} even though, as [[Randall]] points out, such things are pretty much ubiquitous.

==Transcript==

:[Ponytail and Cueball are talking to each other. They are standing between two tables with equipment scattered on them, including lens-stands and eye-protection. Ponytail is pointing away from Cueball towards an unidentified off-panel location.]

:Ponytail: The spectrometer is over here, the Nd:YAG lasers are over here,
:Ponytail: and in the corner is a laser that turned out not to be useful for us, but we keep it because it's fun to toast marshmallows with it.

:[Caption below the panel]
:Every lab in every field has some piece of equipment like this.

{{comic discussion}}
[[Category:Science]]
[[Category:Food]]

2502: Every Data Table

2021-08-14T04:18:51Z

198.41.238.107: /* Explanation */

{{comic
| number = 2502
| date = August 13, 2021
| title = Every Data Table
| image = every data table.png
| titletext = "I'm hoping 2022 is relatively normal because I don't know what symbol comes after the asterisk and the dagger."
| imagesize =
}}

==Explanation==
{{incomplete|Created by ASTERIX and OBELIX. Do NOT delete this tag too soon.}}
This comic is part of a series of comics about the COVID pandemic

The COVID pandemic has had a large impact on the entire world and one way this can be seen is through strange stats resulting from the effects of the pandemic. Various statistics such as employment statistics, spending power, holiday miles, pet ownerships, births (or at least conceptions) and — naturally — deaths may have been either grossly suppressed/increased for the majority of 2020, and for 2021 may have hardly recovered, partially recovered, renormalised, bounced back with a vengeance or be over-compensated for in the effort to catch up.

It is hard to know what 2022 might be like. Nothing (at the time of this comic being published) is exactly back to normal and proper recovery or the resulting compensatory readjustment may not have concluded in time for 2022 to reflect the trends expected based upon pre-2020 figures, and the additional further years that future statistics will record.

As an example, the four-year rolling average of total number of Olympic Games per year (normally a steady 0.25, 0.5, 0.75 or 1, depending upon whether the Winter Olympics and/or (Winter) Paralympics are included) will actually show a discrepancy for the next few years of a type not seen since the 1990s (when the all the Winter games were shifted away from the Summer games' years), the 1960s (the start of the Summer Paralympics) or the 1940s (the last major interuption in the main Summer Olympic cycle).

Sometimes punctuation such as an asterisk (*) or a dagger (†, also called an obelisk) is used to denote an unusual entry in a table to be explained in a footnote with a matching symbol. Common symbols that are used if the first two are taken include multiple asterisks (such as ** or ***), or a series of further symbols such as a double dagger (‡), the section symbol/silcrow (§), the parallel/double-pipe (‖) and the paragraph symbol/pilcrow ( ¶ )and double asterisk (**).

The author, however, seems to have forgotten the potential monkey's paw nature of his wish. Relative is a relative term. It could well be that the whole pandemic thing becomes the new normal, thus removing the necessity of using symbols to delineate such years.

== Transcript ==

:2017....... (scribble)
:2018....... (scribble)
:2019....... (scribble)
:2020*...... (scribble)
:2021†...... (scribble)
:2022....... (scribble)
:2023....... (scribble)
:2024....... (scribble)

Every data table from now on

{{comic discussion}}

[[Category:COVID-19]]

Talk:2435: Geothmetic Meandian

2021-07-28T01:33:34Z

198.41.238.107:

Oh, this one's good. Just checked in (no, I wasn't hovering over the refresh button, my first visit today!) and one glance had me in paroxysms of laughter. But how to explain it? Gonna have to think about that. [[Special:Contributions/141.101.98.96|141.101.98.96]] 01:12, 11 March 2021 (UTC)

I made a really bad spreadsheet to understand better how it works: https://docs.google.com/spreadsheets/d/1fqmHwDmirJrsKPdf94PutFDw31DMAYxNeR7jef1jneE/edit?usp=sharing

Someone fix my ''awful'' transcript edits please. --[[User:Char Latte49|Char Latte49]] ([[User talk:Char Latte49|talk]]) 02:31, 11 March 2021 (UTC)

Seeing the Python added to the Explanation, try this Perl (typed straight here, so not tested)...
## Your prefered variations of "#!/usr/bin/perl", "use strict;" and "use warnings;" here! ##
sub F { my (@vals)=@_; my $invVals=1/int(@vals);
my ($geo,$arith,$med)=(1); # Only defining $geo, so first *= works correctly!
while (@vals) { my($lo,$hi)=(shift @vals,pop @vals); # $hi may be undef - this is intended!
$arith+=$lo; $geo*=$lo; unless (defined $hi) { $med = $lo; last }
$arith+=$hi; $geo*=$hi; unless (@vals) { ($med)=F($lo,$hi) }
}
return ($arith*$invVals, $geo**$invVals, $med);
}
sub GMDN { my (@vals)=sort @_; my $lim=10**(-5); # Adjust $lim to taste...
return "Error: No vals!" unless @vals; # Catch!
return $vals[0] unless ($vals[$#vals]-$vals[0]) > $lim;
return GMDM(F(@vals));
}
my @test=(1,1,2,3,5);
print "Values: @test\nGeothmetic Meandian: ".GMDN(@test)."\n";
...debugged in my head, so probably fatally flawed but easily fixed/adapted anyway. [[Special:Contributions/141.101.99.109|141.101.99.109]] 03:04, 11 March 2021 (UTC)

Why so complicated?
perl -e 'use strict; use warnings; sub F { my ($s,$p) = (0,1); my @srt = sort {$a<=>$b} @_; for (@_) { $s += $_; $p *= $_; } return ($s/@_,$p**(1/@_),$srt[$#_/2]); } sub Gmdn { print join(", ",@_=F(@_)),"\n" for 0..20; return @_; } print join(", ",Gmdn(1,1,2,3,5)),"\n";'
(With interim results) SCNR -- [[User:Xorg|Xorg]] ([[User talk:Xorg|talk]]) 03:18, 11 March 2021 (UTC)
:''I'' can read your version (and I see you do explicit {$a<=>$b}, which indeed ''may'' be necessary in mine for real use, along with additional sanity checks, I will check later) but I wanted to make mine neat, and ''slightly'' tricksy in implementation, but still not quite so entirely obfuscated to the more uninitiated. TIMTOWTDI, etc, so I like your (almost) bare-bones version too. ;)
:(Is 20 cycles enough to converge in sufficiently extreme cases? Won't give "Too deep" error, though, even if it takes at least that long. There's a definite risk that mine might, as written.) [[Special:Contributions/141.101.99.229|141.101.99.229]] 03:45, 11 March 2021 (UTC)
::Given the lack of precision in Randall's example usage, I think 20 cycles ought to be enough for everyone ;-P. I'm trying to prove that the interval's size has to shrink by somewhat close to a factor of 1/2 every cycle, but it's tricky and it's late. If I can assume a factor of 1/2 in the long run, 64 iterations should pin down a 64-bit float.
::I actually didn't try to obfuscate, I was just too lazy to type more ;-). Otherwise I might have left out the "return"s and passing parameters at all. -- [[User:Xorg|Xorg]] ([[User talk:Xorg|talk]]) 04:21, 11 March 2021 (UTC)
:::I find the one-liner more readable: it's straightforward and pretty minimal. For what its worth, here's my version: <pre>perl -MList::Util=sum,product -E 'sub F { (sum @_)/@_, (product @_)**(1/@_), (sort { $a <=> $b } @_)[$#_/2] } $, = " "; say @v = @ARGV; say @v = F(@v) for 1..30' 1 1 2 3 5</pre> 30 iterations is enough for the numbers to display identically on this system (to 14 decimal places). I think it's even cleaner in Raku (formerly Perl 6): <pre>raku -e 'sub F(@d) { @d.sum/@d, [*](@d)**(1/@d), @d.sort[@d/2] }; say my @v = +«@*ARGS; say @v = F(@v) for 1..33' 1 1 2 3 5</pre> On this system, Rakudo yields an additional decimal place, which takes another 3 iterations to converge. [[User:Smylers|Smylers]] ([[User talk:Smylers|talk]]) 06:53, 11 March 2021 (UTC)

Side-thought: is GMDN (nowhere near as logical an ETLA contraction of the title term as, say, 'GMMD' or 'GTMD') actually an oblique reference to the GNDNs as popularised/coined by Trek canon? Worth a citation/Trivia? [[Special:Contributions/162.158.158.97|162.158.158.97]] 04:12, 11 March 2021 (UTC)

Besides of nerdgasm is there some reason why the program code is relevant for the explanation? [[User:Elektrizikekswerk|Elektrizikekswerk]] ([[User talk:Elektrizikekswerk|talk]]) 08:55, 11 March 2021 (UTC)
:Apparently not. I moved it to the trivia section. [[User:Elektrizikekswerk|Elektrizikekswerk]] ([[User talk:Elektrizikekswerk|talk]]) 07:51, 12 March 2021 (UTC)

I do not agree with the statement that "The title text may also be a sly reference to an actual mathematical theorem, namely that if one performs this procedure only using the arithmetic mean and the harmonic mean, the result will converge to the geometric mean." Could one produce a reference to this result? A simple computer experiment does not show this "theorem" to be true, i.e. for the procedure to return the geometric mean of the original entry. [[User:Pointfivegully|Pointfivegully]] ([[User talk:Pointfivegully|talk]]) 15:04, 12 March 2021 (UTC)

= Here is a reference https://math.stackexchange.com/questions/1734978/computing-square-roots-with-arithmetic-harmonic-mean. You must have made a mistake in your computer experiment. As an example, see the details I posted about Cueball and Megan exchanging dollars and euros. This is actually a handy way to compute square roots by hand.

== Proof of convergence ==

Can any of you come up with a mathematical proof that repeated application of F on a set of (say) positive real numbers is guaranteed to converge toward a single real number, i.e. that the GMDN of a set of positive real numbers is well-defined?

One observation I've made is that if you consider that maximum and minimum numbers in the original set to be x1 and xn (without loss of generality), something we know for sure is that AM(x1, ..., xn), GM(x1, ..., xn) and Median(x1, ..., xn) are all at least x1 and at most xn that is to say...

x1 <= AM(x1, ..., xn), GM(x1, ..., xn), Median(x1, ..., xn) <= xn

So range(AM(x1, ..., xn), GM(x1, ..., xn), Median(x1, ..., xn)) is necessarily <= range(x1, ..., xn).

And given that we know that unless x1, ..., xn are all equal, that x1 < AM(x1, ..., xn) < xn, we have an even stricter result (unless x1, ..., xn are all equal) that is
range(AM(x1, ..., xn), GM(x1, ..., xn), Median(x1, ..., xn)) < range(x1, ..., xn).

So, it's clear that range(x1, ..., xn) > range(F(x1, ..., xn)) > range(F(F(x1, ..., xn))) > range(F(F(F(x1, ..., xn)))) > ... and it's also clear that all of these ranges are >= 0. There is a result in number theory that says that any infinite sequence of real numbers which monotonically decreases and is bounded from below converges.

So we know for sure that range(F(F(...F(x1, ..., xn)...))) converges but we still have to show that it converges to 0 to show that the GMDN converges to a single real number.

I'm not sure how to proceed. Does anyone have any ideas?

EDIT:
I just noticed that unless x1, ..., xn are all equal, AM(x1, ..., xn) is at least ((n-1)/n) * range(x1, ..., xn) away from both x1 and xn. So not only do we have that range(x1, ..., xn) > range(F(x1, ..., xn)) from before, but we also have that ((n-1)/n) * range(x1, ..., xn) >= range(F(x1, ..., xn)). This guarantees that that the range falls exponentially on repeated applications of F. So it's certain that the the range ultimately converges to 0, and hence that the GMDN is well-defined.

It might be a good idea for someone to concretely present this idea as a proof on Page.

See my additional notes below. -Ramakarl

[[Special:Contributions/172.69.135.44|172.69.135.44]] 05:07, 11 March 2021 (UTC) Anirudh Ajith

:That doesn't quite work as it stands, since proving AM is that distance away does not say anything about the other two averages. I think it's true, but a little more rigour is required. [[Special:Contributions/141.101.98.120|141.101.98.120]] 09:17, 11 March 2021 (UTC)

When trying this myself I first arrived at 2.082, not 2.089. What threw me off was the incomplete formula for the median, which only works with sorted lists. The three values returned by F(...) aren't necessarily sorted.
[[Special:Contributions/141.101.76.194|141.101.76.194]] 09:49, 11 March 2021 (UTC)

<pre>
First: almost all invocations are with exactly 3 arguments (The output of the previous invocation), so we don't have to deal with N inputs at all.
Notation: In iteration n we have the values min[n] <= mid[n] <= max[n] (in any order) and can compute AM[n], GM[n] (and median[n] = mid[n]).
Let Q[n] := max[n]/min[n] >= 1, R[n] := max[n]-min[n] = (Q[n]-1)*min[n].
We already established that R is decreasing and min is increasing, so Q is decreasing.

Theorem: There is an n0 with R[n+1] <= R[n]*2/3 for all n > n0.

Proof (by case discrimination for each n):
case 1: mid[n+1] != AM[n]:
R[n+1] <= Max(max[n]-AM[n],AM[n]-min[n])
= Max(max[n]*3-(max[n]+mid[n]+min[n]),(max[n]+mid[n]+min[n])-min[n]*3)/3
= Max(max[n]*2-(mid[n]+min[n]),(max[n]+mid[n])-min[n]*2)/3
<= (max[n]-min[n])*2/3
= R[n]*2/3
Hence: R[n+1] <= R[n]*2/3

case 2: mid[n+1] == AM[n]:
because GM <= AM: min[n+1] = GM[n], max[n+1] = mid[n]
Q[n+1] = mid[n]/GM[n]
= (mid[n]^3/(max[n]*mid[n]*min[n]))^(1/3)
= (mid[n]^2/(max[n]*min[n]))^(1/3)
<= (mid[n]/min[n])^(1/3)
<= Q[n]^(1/3)
R[n+1] = (Q[n+1]-1)*min[n+1]
<= (Q[n]^(1/3)-1)*GM[n]
<= (Q[n]^(1/3)-1)*(max[n]^2*min[n])^(1/3)
= (Q[n]^(1/3)-1)*Q[n]^(2/3)*min[n]
= (Q[n]-Q[n]^(2/3))*min[n]
= R[n]-(Q[n]^(2/3)-1)*min[n]
<= R[n]-(Q[n]-1)*min[n]/(Q[n]^(1/3)+1))
= R[n]-R[n]/(Q[n]^(1/3)+1)
= R[n]*(1-1/(Q[n]^(1/3)+1))
Now we can pick a q1 = Q(n1) with q1 > Q[n] >= 1 for n > n1 because Q is decreasing:
R[n+1] <= R[n]*(1-1/(q1^(1/3)+1))

Together with case 1, this gives R -> 0 and thus Q -> 1. So we can pick another q0 = Q(n0) with q0 <= 8:
R[n+1] <= R[n]*(1-1/(q0^(1/3)+1)) <= R[n]*2/3
</pre>
-- [[User:Xorg|Xorg]] ([[User talk:Xorg|talk]]) 17:34, 11 March 2021 (UTC)

== Better Python implementations ==

I'd like to add a somewhat more compact Python implementation based on the numpy module.
import numpy as np

def F(x):
return np.mean(x), np.exp(np.log(x).mean()), np.median(x)

def GMDN(x, tolerance=1e-6):
while np.std(x) > tolerance:
x = F(x)
return x[0]

gmdn = GMDN([1, 1, 2, 3, 5])
print(gmdn)
--[[User:Lvdgraaff|Lvdgraaff]] ([[User talk:Lvdgraaff|talk]]) 10:42, 11 March 2021 (UTC)

No need for numpy, there's the statistics module in the stdlib

import math
import statistics

def F(*nums):
return (
statistics.mean(nums),
statistics.geometric_mean(nums),
statistics.median(nums),
)

def GMDN(*nums):
while not math.isclose(max(nums), min(nums)):
nums = F(*nums)
return nums[0]

gmdn = GMDN(1, 1, 2, 3, 5)
print(gmdn)

:For something as simple as this, I always find it cheating to use a package to abstract away the few actually necessary calculations. You might as well use a DWIM module and do 'result = DWIM(input)' as the sole command. But that's me for you. I'd write my own direct-to-memory screen RAM accesses, if silly things like OS HALs and GPU acceleration (once you find a way to message them as directly as possible) hadn't long since made that pretty much moot, if not actually verboten... [[Special:Contributions/141.101.99.109|141.101.99.109]] 17:53, 11 March 2021 (UTC)

I'd like to add my own implementation:

from math import *
def getMeans(n=list):
n.sort()
mean=sum(n)/len(n)
if len(n)%2==1:
median=n[len(n)//2]
else:
median=(n[1+floor(len(n)/2)]-n[floor(len(n)/2)])/2
prod=1
for i in n:
prod*=i
gmean=prod**(1/len(n))
return [mean,median,gmean]
def gmdn(tol,n=list):
mList=n
mList=getMeans(mList)
while not (isclose(mList[0],mList[1],rel_tol=tol) and isclose(mList[1],mList[2],rel_tol=tol) and isclose(mList[0],mList[2],rel_tol=tol) ) :
mList = getMeans(mList)
return (mList[0]+mList[1]+mList[2])/3

print(gmdn(1e-15,[1,1,2,3,5]))

which gives me 2.089057949736859

== Sloppy notation? ==

As a mathematician, I immediately noticed a couple of annoying niggles. Firstly, it is only implied, but never clearly stated, that the input list is ordered - which means the median is wrong unless ordered. Now F outputs an ordered triple of real numbers, and in calculating G, this is fed in to F again directly. This will frequently give inputs that are not in order, and in subsequent iterations the "median" will always be the middle number - i.e. the geometric mean - regardless of the actual median. Secondly, Randall's final line gives the output of G as a single number, but as it is just the result of a repeated application of F, the output of G should be an ordered triple. I'm sure Randall is aware of both, and chose to cut out the implied ordering of the inputs and choosing one of the three values as the output of G as they aren't necessary for the joke, but maybe we should note something about this in the explanation.[[Special:Contributions/141.101.99.109|141.101.99.109]] 13:07, 11 March 2021 (UTC)
:First, I've never seen a definition of median which doesn't account for ordering itself, although I am a little annoyed at his definition for a different reason— that it doesn't account for even-length lists. Second, what I got from the comic initially is that GMDN is supposed to be a single number, specifically that value for which all three of its elements would become equal if implemented infinitely many times (and it ''will'' converge, because if the three elements are all the same it already has converged, and if at least two are different, both means will necessarily become greater than the least value and smaller than the greatest value due to the definition of 'mean'). Another annoyance I noted is that GMDN is real iff there are an even number of negative numbers and/or the length of the initial list is odd, but I suppose that can't be helped. Ooh, complex meandianing! [[User:BlackHat|BlackHat]] ([[User talk:BlackHat|talk]]) 15:15, 11 March 2021 (UTC)
::I guess it depends on whether we take x_{(n+1)/2} literally or not. If taken literally, the elements need to be sorted, and even-length lists don't work. If we assume the "median" is the literal part, and the notation is just a simplified sketch, then both are okay (median of even list is average of the two "middle" elements). [[Special:Contributions/172.68.143.160|172.68.143.160]] 22:00, 12 March 2021 (UTC)

== Is the arithmetic-geometric mean connected to geometry? ==

In the case that only the arithmetic and geometric mean are used the combined arithmetic-geometric mean can be interpreted as the radius R of a circle which has the same circumference as an ellipse with half axes a and b.

R = M(a,b)

Can the Geothmetic Meandian be interpreted are the radius R of a 3D sphere which has the same surface as an elliptic cylinder with half-axes a and b and length c ?

R = GMDN(a,b,c)

: Here is a geometric interpretation of the inequality between them: {{w|Inequality_of_arithmetic_and_geometric_means#Geometric_interpretation}}. [[User:Danloeb|DanLoeb]] ([[User talk:Danloeb|talk]]) 19:31, 14 March 2021 (UTC) D--[[User:Danloeb|DanLoeb]] ([[User talk:Danloeb|talk]]) 19:31, 14 March 2021 (UTC)

=== The RandallMunroe Set ===

Here is some MATLAB code (sorry) to generate an image showing the number of cycles required to converge, a' la' the Mandelbrot Set.
Not sure how to post an image here, but it is really cool.

% RandallMunroeSet.m
% From a suggestion by Randall Munroe in XKCD #2435 Mar 10 2021
% new statistic GMDN(x) = [mean(x), geomean(x), median(x)]
% calculation is recursive, ending when converged
% here we count the cycles required to converge and plot a' la' Madelbrot Set
% the initial X input can be any length vector, but we restrict to 3 space
% here for visualization, and fix Z so we get a 2D image
% so far, for positive values, it converges in less than 40 or not at all
% for negative x, set max cycles to something larger like 60
% I haven't plotted it, but there is logically another set that plots the
% resulting converged value.
% Explore!
% (c)2021 CC BY-NC 2.5 SBStevenson@uh.edu peace, love, trees

% here we answer the question, how many cycles does it take for GMDN to
% converge?
maxcycles = 40; stepsize = .0025;
z = 1; % pick a Z, any Z
x = stepsize:stepsize:(4-stepsize); % explore a range of x and y
y = x;
wbh = waitbar(0);
RMS = zeros(numel(x),numel(y),numel(z)); % no, not root mean square, this is the Randall Munro Set!

for idx = 1: numel(x)
waitbar(idx ./ numel(x)); % feedback on progress
for jdx = idx:numel(y) % result is symmetric across the diagonal, so we save time by computing above the diagonal

for kdx = 1:numel(z)
RMS(idx, jdx, kdx) = gmdn([x(idx),y(jdx),z(kdx)], maxcycles);
RMS(jdx, idx, kdx) = RMS(idx, jdx, kdx); % copy across the diagonal
end
end
end
close(wbh)
RMS = min(maxcycles,RMS);

if numel(z) == 1;
figure(420);
image(255*RMS./maxcycles);truesize; colormap(jet(256));
end
if numel(z) == 3; % allow for true color, but in practice it is so sensitive to initial z value it just gives three different sets unless the Zs are VERY CLOSE
figure(420);image(RMS./maxcycles);truesize;
end
title(['RandallMunro Set Z = ' num2str(z)]);

figure(3);hist(RMS(:),0:maxcycles);
%% How many cycles to converge?
function ncycles = gmdn(x, maxcycles)
ncycles = 0;
while ncycles < maxcycles
ncycles = ncycles + 1;
x = [mean(x), geomean(x), median3(x)];
if all(x(1) == x(2:3))
break
end
end

end

%% Geometric Mean
function result = geomean(x)
result = prod(x) .^ (1/numel(x));
end

%% Slightly faster median than builtin MATLAB function
function result = median3(x)
y = sort(x);
result = y(2);
end

My python program:
from math import *
def getMeans(n=list):
n.sort()
mean=sum(n)/len(n)
if len(n)%2==1:
median=n[len(n)//2]
else:
median=(n[1+floor(len(n)/2)]-n[floor(len(n)/2)])/2
prod=1
for i in n:
prod*=i
gmean=prod**(1/len(n))
return [mean,median,gmean]
def gmdn(tol,n=list):
mList=n
mList=getMeans(mList)
while not (isclose(mList[0],mList[1],rel_tol=tol) and isclose(mList[1],mList[2],rel_tol=tol) and
isclose(mList[0],mList[2],rel_tol=tol) ) :
mList = getMeans(mList)
return mList[0]
print(gmdn(1e-15,[1,1,2,3,5]))

It gave me 2.0890579497368584

== Proof - Possibly by Induction ==

Earlier question:
> Can any of you come up with a mathematical proof that repeated application of F on a set of (say) positive real numbers is guaranteed to converge toward a single real number

Define: 
F(n) = {An,Bn,Cn} 
F(n+1) = {An+1, Bn+1, Cn+1} = {ave(An,Bn,Cn), geomean(An,Bn,Cn), median(An,Bn,Cn)} 
R(n) = range of F = max(An,Bn,Cn)-min(An,Bn,Cn), for iteration n 
We want to show that the range R(n) converges to 0. 
With the following notation: max(n) == max(An,Bn,Cn), ave(n)==ave(An,Bn,Cn), .. 
We observe the following emperically for many different inputs: 
R(n) = max(n)-min(n) 
CASE 1: max(n)=ave(n), THEN max(n+1)=median(n+1)=geomean(n) AND min(n+1)=geomean(n+1) 
In this case max(n+1) is fixed to a previous value, the geomean(n), and min(n+1) takes on the new geomean(n+1) which is guaranteed to reduce the range R(n) as min(n) < geomean(n+1) < max(n). It also implies case 2 must be invoked because min(n+1)=geomean(n+1) at n+1. 
CASE 2: min(n)=geomean(n), THEN max(n+1)=ave(n+1) AND min(n+1)=median(n+1)=ave(n) 
In this case min(n+1) is fixed to a previous value, the ave(n), and max(n+1) takes on the new ave(n+1) which is guaranteed to reduce the range R(n) as min(n) < ave(n+1) < max(n). It also implies case 1 must be invoked because max(n+1)=ave(n+1) at n+1. 
 
Each case forces the range to be reduced while also forcing the alternate case on the next iteration. 

In other words, the maximum at each iteration alternates between the average and the median, and the minimum alternates between the geomean and the median. Thus either the minimum or the maximum at n+1 are always converging away from the minimum and maximum at previous n. 
While this is not a formal proof, since the initial observations are emperical, I believe that a proof-by-induction can be built based on the oscillating convergence (without the need for F to be differentiable). 

[[User:Ramakarl|Ramakarl]] ([[User talk:Ramakarl|talk]]) 00:00, 12 March 2021 (UTC)

:How can this be formulated as a PDE when F isn't even differentiable?
:Besides, R(Fn+1) < R(Fn) does not imply limit R(Fn) = 0 (Think R(n) := 1+1/n). -- [[User:Xorg|Xorg]] ([[User talk:Xorg|talk]]) 02:50, 12 March 2021 (UTC)
Agreed. F is not differentiable due to median. For arbitrary R(n) such as R(n)=1+1/n then limit R(Fn) != 0, however I do not define R(n) arbitrarily but define it as R(n)=max(An,Bn,Cn)-min(An,Bn,Cn) [[User:Ramakarl|Ramakarl]] 

[[User:snark]]
This has nothing to do with a PDE or the heat equation. It is an iterative map from R^3 to R^3 (after the first application of F). In
order to prove it converges you need to show that there is a fixed point and that the mapping takes you closer to it. The fixed points
are easy since F((x,x,x))=(x,x,x) so there is a line of fixed points. You can then calculate the perpendicular distance between the
starting point (x1,x2,x3) and the line given by (x(t),x(t),x(t)). Next you calculate the distance between f((x1,x2,x3)) and the line
and show that is is less than the first distance.

Agreed. I've removed reference to PDE or Heat equation except for the indirect similarity. The new suggestion for proof, which is incomplete, is inductive based on the observed alternation of the min/max between the geomean and arithmean. I believe it can be shown that for some N, there exists F(N)=k, where k=min(N)=max(N)=arithmean(N)=geomean(N)=median(N) within some epsilon, and k is the fixed point. This is because the min(n+1), median(n+1) and max(n+1) alternate between arithmean(n) and geomean(n), which are strictly inside the open interval ( min(n), max(n) ). [[User:Ramakarl|Ramakarl]]

I believe we can produce a simpler, rigorous proof. Assuming a set of three is given, we can show that after every 2 iterations, the range is reduced by at least 1/3 of its original value, and therefore it converges exponentially to 0. We use the fact that each iteration, none of the three values will lie outside the range of the previous iteration. In addition, it can be shown that the arithmean lies at least 1/3 of the previous range away from the highest and lowest values of the previous iteration.

If the arithmean is the highest or lowest value on the first iteration, then the range will therefore already be small enough (and won't get bigger in the second iteration.) Otherwise, the only remaining option is that it is the middle (median) value. So on the second iteration, both the median and the arithmean are within the reduced 1/3 range, and at least one of them must be the highest or lowest value. The range will always be the required size.

Edit: Note that this proof holds only assuming the values are nonnegative. Some sets of values including negative ones, such as gmdn(-4,-4,1), do not converge.
[[Special:Contributions/141.101.98.16|141.101.98.16]]

== Why is this funny? ==
Wow, paragraphs and paragraphs of explanation, and calculations, and computer code describing everything about the XKCD comic.
I am impressed with how much people know. After all that explanation, can anyone tell me if there is anything comical about this comic?
Aside from the fact that Randal is combining formulas that don't usually get combined, is there anything here that strikes anyone as funny? The previous one about people asking absurd questions about what they could do after they are vaccinated had me laughing out loud. Can anyone tell me that they laughed at this comic and what was funny? Thanks. [[User:Rtanenbaum|Rtanenbaum]] ([[User talk:Rtanenbaum|talk]]) 01:56, 12 March 2021 (UTC)
:YMMV, but I found it funny because I just spent the last fortnight teaching how to find mean (and median, and quartiles for that matter) to 15/16yrolds. And they found that hard enough. I did not inform them of Geometric mean. I guess it's funny to me because it's such a long reach. [[User:Thisfox|Thisfox]] ([[User talk:Thisfox|talk]]) 02:48, 12 March 2021 (UTC)
::No, the joke is quite clearly explained in the text below the formula: "Pro Tip: If in doubt just mash them together". [[User:Elektrizikekswerk|Elektrizikekswerk]] ([[User talk:Elektrizikekswerk|talk]]) 07:53, 12 March 2021 (UTC)
::As I'm currently supposed to be working someone else should please add this with a proper formulation. I just re-added the incomplete tag. [[User:Elektrizikekswerk|Elektrizikekswerk]] ([[User talk:Elektrizikekswerk|talk]]) 08:00, 12 March 2021 (UTC)
:: @Rtanenbaum funny you should give previous comic as example, as it is funny for exactly the same reason: using absurdity. The only difference is *most* people will get it why it is absurd to ride bicycle down the stairs in someones house (while it is OK to use bike outside, and it is OK to visit if you're vaccinated and thus use the stairs in someones house, BUT it is combining those unrelated activities that is absurd). Same thing here, only it requires some math background: using median has its uses, as does using geometric and arithmetic means, but it is combining them in this fashion that is absurd. And especially the recommendation to "mash mathematical functions you obviously don't understand as substitute to choosing correct one" is absurd. It is like you don't know you have to ADD prices of items on your receipt to calculate the total, so someone recommended you to use some random combination of mathematical operations to calculate the total. (with a added twist that suggested combination would return some result which is not far off the calculation). In addition, the fact that some people do not understand why it is funny (so might take such absurd recommendation seriously) makes it even more funny.--[[Special:Contributions/172.68.221.46|172.68.221.46]] 09:49, 12 March 2021 (UTC)
::Apparantly someone deleted the tag again without giving a further explanation... I will undo this change. [[User:Elektrizikekswerk|Elektrizikekswerk]] ([[User talk:Elektrizikekswerk|talk]]) 09:58, 12 March 2021 (UTC)
:::'Twas not I, but note that this is 'explainxkcd' not 'explainwhyxkcdisfunny'. I think we both recognise that a cornucopia of details have been explained. It is even funnier to see someone insisting we continue to dissect the frog, but I'm not sure I need to fully explain that. ;) [[Special:Contributions/162.158.159.108|162.158.159.108]] 15:16, 12 March 2021 (UTC)
:Yes, here's a bit more on that.. I agree with [[User:Elektrizikekswerk|Elektrizikekswerk]] the joke is explained. The stat tip: "If you aren't sure whether to use the mean, median or geometric mean, just calculate all three, then repeat until it converges." is funny because there are many situations in the physical sciences where the arthmean, geometric mean and median for some data are different values. It is perhaps common that scientists not well versed in statistics are unsure which to use. The funny bit is imagining this less-statistically-versed-scientist throwing up their hands and just accepting the fixed constant given by iterating GMDN as the 'answer' irrelevant of any physical meaning. Also the name "geothmetic meandian" is funny because the word meandian is similar to both median, which it uses, and to ''meander'' which is indicated by the alternate assignment of the median on each iteration -- informally, this function meanders. [[User:Ramakarl|Ramakarl]]
:Thanks to all who shared the absurdity so I could also enjoy the joke, and the joke is on me for needing to have a joke "explained". Now where is the button for me to give credit to the best answer? I want to be sure you get points toward your next-level badge. ;-) [[User:Rtanenbaum|Rtanenbaum]] ([[User talk:Rtanenbaum|talk]]) 16:23, 13 March 2021 (UTC)
:This is actually one of my favorite xkcd comics. Even before seeing this comic, one thing I would always do was take the AM(AM,GM) instead of using either average on it's own. [[User:nullcline|nullcline]] ([[User talk:nullcline|talk]]) 17:33, 20 July 2021 (UTC)

== PyPi-package ==
I made a PyPi-package, if anyone (for some God-forsaken reason) want to use this without implementing it (ya lazy gits): https://pypi.org/project/GMDN/ [[User:BollaBerg|BollaBerg]] ([[User talk:BollaBerg|talk]]) 15:03, 15 March 2021 (UTC)

== Proof - extension to negative values ==

As others have proven, the geothmetic meandian converges for <code>a,b,c > 0</code>.

Case <code>a==0, b,c>=0</code> (and permutations):
: then the geometric mean will always be 0. All derivations for <code>a,b,c > 0</code> still apply, thus the set always converges to 0.

Case <code>a,b,c <= 0</code>:
: <code>arithmean(a,b,c) == -arithmean(-a,-b,-c)</code>; the same holds for the median and the geometric mean. Thus convergence is given, with the absolute value of the result the same as for positive inputs.

Case <code>a<0, b,c>0</code>, Case <code>a,b<0, c>0</code>
: the geometric mean is negative iff 1 or 3 inputs are negative.
: the median is negative iff 2 or 3 inputs are negative.
: thus, any mixed sign input will yield a mixed sign output.
: thus, '''if''' the geothmetic meandian converges for mixed-sign inputs, the limit has to be +-0.
: unfortunately, the proof by 141.101.98.16 does not hold here unmodified: it relies on the next set always being within the range of the previous set. This is not true for the geometric mean with mixed-sign inputs. E.g. <code>geommean(-1,2,4)=-4</code>.
: However, what does hold is that geometric mean is always within the extended range of <code>+- max(abs(inputs))</code>.
: this is not yet sufficient proof.
[[User:Xlf|Xlf]] ([[User talk:Xlf|talk]]) 18:05, 15 March 2021 (UTC)

Given <code>Mn := max(abs(inputsn))</code> and <code>minn < 0 < maxn</code>, we still have <code>abs(AMn) ≤ Mn*2/3</code> (by dropping a summand with different sign from AMn), <code>abs(AMn+1) ≤ Mn+1*2/3 ≤ Mn*2/3</code> and <code>abs(midn+1) ≤ abs(AMn) ≤ Mn*2/3</code>, because AMn shares a sign with one of the others. <code>abs(GMn+1) = abs(GMn*midn*AMn)(1/3) ≤ Mn*(1*1*2/3)(1/3) ≤ Mn*(2/3)(1/3)</code>.
Consequently <code>Mn+2/Mn ≤ (2/3)(1/3)</code>, which shows convergence to 0. □ -- [[User:Xorg|Xorg]] ([[User talk:Xorg|talk]]) 16:43, 31 March 2021 (UTC)

Edit: Deleted comment. Sorry for the accidental spam. [[User talk:Quillathe Siannodel|{)|(}]][[User:Quillathe_Siannodel|Quill]][[User talk:Quillathe Siannodel|{)|(}]] 14:54, 25 March 2021 (UTC)
:The joke is still not explained, as far as I can tell. Maybe it's too obvious but since people asked (see three sections above in the comments) I think the explanation of the actual joke shoudl be added. As I too find it quite obvious what the joke is I find it hard to really explain it which is the reason why I didn't. Besides of that, the incomplete tag actually says why it's incomplete (in this case). AND there is already a comment section (again, three sections above) about this problem. [[User:Elektrizikekswerk|Elektrizikekswerk]] ([[User talk:Elektrizikekswerk|talk]]) 07:41, 26 March 2021 (UTC)
::Sorry. That wasn't a thing when I added this section.

can someone help me with my python code of this? i dont get why this isnt working! https://replit.com/@Bumpf/geothmetic for my code. if you want i can paste my code here. i also commented in the code the error and why i dont understand it. thank you in advance! (also the geometric formula thing in the table on the page is showing a big red error. Maybe fix that?) [[Special:Contributions/172.70.38.56|172.70.38.56]] 13:35, 26 March 2021 (UTC)Bumpf

Since it uses F(F(F...)) someone should write a Hascal version that actually uses the fixedpoint function. [[Special:Contributions/172.69.35.175|172.69.35.175]] 22:56, 30 March 2021 (UTC)