Wikipedia talk:WikiProject Mathematics/Archive/2020/Nov

MOS:MATH#Blackboard bold

This section of the manual of style does not takes into acoount the improvement (over the years) of the rendering of Latex in WP, nor the fact that the use of blackboard bold for the basic number systems is presently a standard in mathematical articles. Also, the rendering in Unicode of blackboard bold is definitely awful, even when using {{math}} environment (see, for example, Quaternion#Algebraic properties).

So, I have written a new version of this section that can be found at user:D.Lazard/Blackboard. My question is: is this new version worth to replace the old one? In any case, be free to improve my poor English. D.Lazard (talk) 16:50, 1 November 2020 (UTC)

I disagree that blackboard bold for the basic number systems is presently a standard in mathematical articles. You need to prove that. --Trovatore (talk) 18:24, 1 November 2020 (UTC)

I agree that the Unicode blackboard bold is awful and to be avoided. If we are to use blackboard bold for the basic number systems (which I think is pretty common, at least, regardless of whether we can call it "a standard") we should use <math> not templates/html. —David Eppstein (talk) 19:52, 1 November 2020 (UTC)

Right, so there are two rather separate issues, one being whether BBB ought to be encouraged if it rendered perfectly, and one being the current state of rendering.

On the current state, <math> is a lot better than it used to be, but sizing issues can still be a little distracting.

On the more central issue independent of rendering, it's certainly true that there is a considerable amount of published material that uses BBB, especially for the real, natural, and complex numbers.

I learned real analysis from Folland, which uses ordinary bold, and I personally find that more graceful. It is true that there are situations where you might reasonably want to use (say) R as a variable, and in those situations it's useful to have $\mathbb {R}$ available. But in origin $\mathbb {R}$ is just a way of writing R on a blackboard without using so much chalk.

I guess part of what bothers me about wide use of BBB is the danger of contributing to the perception that these sets have once-and-for-all symbols that are used universally, which just isn't true. --Trovatore (talk) 20:06, 1 November 2020 (UTC)

(edit conflict) Blackboard bold is certainly a standard (alongside boldface) that is commonly used in math articles. Just take a look at Annals's most recent issue (Volume 192 Issue 2): 7 of 8 articles used blackboard bold, 1 of 8 articles used boldface. — MarkH₂₁^talk 20:12, 1 November 2020 (UTC)

It's a standard in the sense that it's widely understood. I was probably taking D.Lazard to be saying something more like it was the standard, which may not have been what he meant. But that's really my concern; we should not be promoting it as the standard. --Trovatore (talk) 20:28, 1 November 2020 (UTC)

It might not be the standard (although if it isn't, it's still the clear majority). I don't see the draft at User:D.Lazard/Blackboard as promoting it as the standard though. It says to use the Latex rendering [...] or the standard boldface and discourages the Unicode blackboard bold characters. — MarkH₂₁^talk 20:42, 1 November 2020 (UTC)

Regarding the original question, I think that the draft is a suitable replacement / expansion of the current MOS:MATH#Blackboard bold (perhaps without the mainly in elementary textbooks claim). — MarkH₂₁^talk 20:59, 1 November 2020 (UTC)

Should it mention that $\mathbb {E}$ is sometimes used for expected value? I think it is not as standard, but it does appear in some of our articles, e.g. Pearson correlation coefficient. —David Eppstein (talk) 22:42, 1 November 2020 (UTC)

There are other uses. Some are listed in the current version of List of mathematical symbols, where $\mathbb {A} _{n}$ (for the affine space of dimension n) is omitted. This is by thinking how presenting blackboard bold in the new version of this list that I came to the conclusion that MOS:MATH was definitely of no help for this matter. D.Lazard (talk) 11:52, 2 November 2020 (UTC)

I'm not sure it's useful to say that Blackboard bold typeface was never used in traditional typography. What counts as "traditional"? And the history of blackboard bold is better addressed in the article on it than in the Manual of Style. I'd collapse the first two sentences to Blackboard bold typeface was introduced to more easily distinguish boldface from ordinary lettering on a blackboard. XOR'easter (talk) 19:17, 2 November 2020 (UTC)

In general I don't think the "it was originally intended as synonymous with X but diverged" is useful as guidance on current style. We could say the same about "u" versus "v", or about capital and lower case letters being used together and meaning different things rather than just being different ways of writing the same letters. —David Eppstein (talk) 20:22, 2 November 2020 (UTC)

I guess I think it's sort of bad to use bbb distinctively from bold. How are you going to represent that on an actual blackboard?

Granted that it's not our place to either drive or impede language change. But I think we should err to the conservative side when necessary. --Trovatore (talk) 20:35, 2 November 2020 (UTC)

It's also bad to use letters with curves in them like u instead of v. Because how are you going to chisel that into stone? —David Eppstein (talk) 21:30, 2 November 2020 (UTC)

Blackboards are still in use. --Trovatore (talk) 21:33, 2 November 2020 (UTC)

So are engravings into stone. But not as a medium for viewing Wikipedia articles. —David Eppstein (talk) 22:42, 2 November 2020 (UTC)

My point is that if you're using $\mathbb {R}$ specifically to be able to distinguish it from R, that's probably not an optimal habit to get into, because it'll be difficult to present on a blackboard, even if it works fine in an online resource. Blackboard bold really should be thought of as a way to do bold on a blackboard. Then if you also want to use it in print, fine, but using it distinctively is probably not a great idea. --Trovatore (talk) 22:53, 2 November 2020 (UTC)

If you really think that blackboard bold can only be a way to make boldface look more legible then why do you want to deprive Wikipedia readers of the same benefits of legibility by discouraging its use? Surely it would be more consistent to forbid boldface and just use bbb for everything that you want to embolden. —David Eppstein (talk) 23:14, 2 November 2020 (UTC)

I never said it was a way to make it more legible. I said it was a way not to use so much chalk. (I didn't mention the time it takes to put a bold letter on a chalkboard; that's actually probably even more important than the amount of chalk.) --Trovatore (talk) 23:18, 2 November 2020 (UTC)

So we should avoid a convenient notation in our Wikipedia articles because chalk is expensive? Or because you never learned to use beamer to format projector slides with LaTeX? Those don't seem like particularly principled or relevant objections to me. —David Eppstein (talk) 23:24, 2 November 2020 (UTC)

I do in fact know how to use beamer. It's not great for free-form discussions, though.

Aesthetically it just seems off to use a notation for rendering bold on blackboards as though it were semantically different from bold. It's like using $\phi$ distinctively from $\varphi$. Even if you can come up with situations where that would be convenient, it's still a bad idea. --Trovatore (talk) 23:31, 2 November 2020 (UTC)

Merger of maths rating and maths banner

Look, I am not a participant of the maths project but I like to have the templates {{maths rating}} and {{maths banner}} to be merged into one à la all the WikiProjects. The merged version can be found at Template:WikiProject Mathematics/sandbox and testcases can be found at Template:WikiProject Mathematics/testcases. --Soumya-8974 ^talk _contribs ^subpages 17:49, 22 October 2020 (UTC)

This is feasible at some point in the future, should the project want to. But the code in that sandbox is not quite right, and I would want to check a few things first — Martin (MSGJ · talk) 18:53, 25 October 2020 (UTC)

@Soumya-8974: I think the most sensible direction to merge this in the first instance is to {{maths rating}} as that is the older template with more history. I have added the required quality classes and functionality to Template:Maths rating/sandbox, and Template:Maths banner could potentially be redirected to Template:Maths rating with barely any noticeable change — Martin (MSGJ · talk) 20:48, 1 November 2020 (UTC)

You're right. I proposed to merge {{maths banner}} to {{maths rating}}, delete {{WikiProject Mathematics}} and move {{maths rating}} to {{WikiProject Mathematics}}. --Soumya-8974 ^talk _contribs ^subpages 04:58, 2 November 2020 (UTC)

The first part of this is now done and I will leave it to someone else if they want to open a [WP:RM]] on {{maths rating}} — Martin (MSGJ · talk) 12:13, 3 November 2020 (UTC)

I agree with some kind of merge, it's not clear to me if there is a reason for keeping a separate template for pages outside article space. No comment on how it should be carried out. — MarkH₂₁^talk 20:52, 1 November 2020 (UTC)

Wikipedia:WikiProject Mathematics/Assessment

When I look at Wikipedia:WikiProject Mathematics/Assessment I see a table with 17,771 articles in it. If I look at Wikipedia 1,0 Server - Mathematics I see a similar-but-different table with 20,871 articles in it. It's missing the "unassessed" and "unrated" columns; it adds a few others. Since the total is larger, I assume that the first is many years out of date, and that the second is updated daily. 67.198.37.16 (talk) 17:18, 5 November 2020 (UTC)

Since you are seem to be continuing to edit in areas related to ergodic theory, can I just add a comment on sources? The topic started around 1931–1932 with von Neumann and Birkhoff (working in competition, as you can read from recently published letters). It's probably worth adding more references for ergodicity. I have added a list of citations for ergodic flow, an article which I am currently rewriting to simplify the presentation (flows built under a ceiling function were first invented by von Neumann in his 1932 Annals paper and his construction was essentially operator-theoretic). The books of Petersen, Walters, Nadkarni, Pollicott & Yu and Cornfeld, Fomin & Sinai are all useful references. Unfortunately there is no translation of von Neumann's original paper (George W. Mackey has made summaries of it in his lecture notes). The 1960 book of Jacobs is in German and uses convexity to avoid using the spectral theorem. For invertible measure-class preserving transformations, anything by Rohlin, Furstenburg, Ornstein or Weiss is valuable, particular the material on Bernoulli shifts and entropy: the complete 1966 notes of Rohlin are available on google books. Mathsci (talk) 19:08, 5 November 2020 (UTC)

User:WP 1.0 bot/Tables/Project/Mathematics is updated daily so I have replaced with that one — Martin (MSGJ · talk) 20:33, 5 November 2020 (UTC)

Proposed change to Template:Maths rating from 2018

Per this Phabricator task, User:MusikAnimal in October 2018 requested that this template be changed to use {{WPBannerMeta}} so that the assessments are compatible with XTools. However, it got ignored because there were so few people watching the page, so I'm pointing it out here per the comment. Could someone with template-editing power please take a look at this? Thanks. Ionmars10 (talk) 12:30, 17 September 2020 (UTC)

I'm starting to look into this. If anyone want to as well, please feel free. –Deacon Vorbis (carbon • videos) 13:11, 17 September 2020 (UTC)

I think {{class mask}} is what does the normalization, so it should be enough to simply pass the class value through it when storing it via the #assessment parser function. But converting the whole template to use {{WPBannerMeta}} is better to be consistent with other WikiProject banners. — MusikAnimal ^talk 13:35, 17 September 2020 (UTC)

Yes, please kill this non-standard banner and have {{WikiProject Mathematics}} handle both what {{Maths rating}} and {{Maths banner}} currently do. There is no reason for the two distinct templates. Headbomb {t · c · p · b} 18:19, 22 September 2020 (UTC)

What matters to me on this is that we continue to use the "priority" field rather than "importance". As long as we don't start using "importance", I have no objection. --Trovatore (talk) 18:26, 22 September 2020 (UTC)

You can easily rename the parameter with |IMPORTANCE_SCALE_NAME=priority or something similar (the parameter name might have changed), User:MSGJ would know. Headbomb {t · c · p · b} 00:35, 3 October 2020 (UTC)

Really it ought to be globally renamed to "priority". Calling it "importance" was always an extremely bad choice. But at least for this project, we should uniformly use "priority". --Trovatore (talk) 04:52, 7 October 2020 (UTC)

There is a meta-enabled version in the sandbox and some testcases at Template:Maths rating/testcases. I agree completely with your view of priority/importance and the meta-template supports priority, although sadly yours seems to be the only project still using it. The categories are currently using the lower-case version (priority instead of Priority) but this will be simple enough to fix. — Martin (MSGJ · talk) 12:26, 8 October 2020 (UTC)

Seems to work but does look considerably different. --Salix alba (talk): 19:59, 8 October 2020 (UTC)

What is even the point of the illegibly tiny 10-pixel-or-so head of Blaise Pascal next to the field? Is it there because the space looked empty below the big colored banners for quality and priority? To me it looks worse than having nothing at all there. —David Eppstein (talk) 20:16, 8 October 2020 (UTC)

I have removed the custom size so it now shows the default 25px. Is that better? It can of course be removed altogether. — Martin (MSGJ · talk) 07:57, 9 October 2020 (UTC)

The differences are pretty much cosmetic. One thing though, @MSGJ:, the 'history' thing should probably be handled like another taskforce, rather than be shoved in the 'additional information' part of the template. Headbomb {t · c · p · b} 20:20, 8 October 2020 (UTC)

It seems the |historical= parameter can be set regardless of the field and is independent of |field=history. Is that really desirable? I suppose it would be redundant to use both at the same time. — Martin (MSGJ · talk) 07:57, 9 October 2020 (UTC)

The conversion seems to have gone well. I have a few questions:

• |historical=yes triggers Category:History of subject mathematics articles and |field=history triggers Category:Mathematics articles related to history of mathematics. What is the distinction between these and can they be merged into one?
• |frequentlyviewed= was set by VeblenBot which hasn't edited for several years. Should this feature be dropped?
• Is there ever a need to identify an article as being within more than one field, e.g geometric group theory should probably be tagged as geometry and algebra — Martin (MSGJ · talk) 15:10, 13 October 2020 (UTC)

  History of mathematics is a field of academic study concerning the mathematics of the past. It is a different thing than topics within mathematics which have themselves become historical or obsolete. And yes, whenever there are boundaries, there are boundary cases, topics that cross those boundaries. Topics that cross multiple projects are handled by having multiple banners. Without being able to list articles as being in more than one field how would we handle topics that cross multiple fields within mathematics? —David Eppstein (talk) 16:55, 13 October 2020 (UTC)

  Just as I thought. So instead of using two different banners, which is very clumsy, a better syntax would be {{maths rating|algebra=yes|geometry=yes}}. Do you agree? And thanks for the explanation of the difference between history and historical - I will try and clarify the documentation — Martin (MSGJ · talk) 18:38, 13 October 2020 (UTC)

Page assessments

I'm not quite sure why {{Maths rating}} is not working with XTools. Looking at mw:Extension:PageAssessments for assessment to work it requires the {{#assessment: <name of the wikiproject> | <class> | <importance>}} parser function. Looking at the source of math rating template the necessary code is there. --Salix alba (talk): 08:17, 7 October 2020 (UTC)

Looks like the problem might have been that XTools requires the class/importance values to start with an upper case letter. I've edited the template to ensure this happens and on the couple of pages I've tested the XTools results seem to be working now. See for example XTools|Carry (arithmetic). Other articles will take longer for the job queue to do its job. If you want to hurry things along a null edit will make things change instantly. --Salix alba (talk): 09:20, 7 October 2020 (UTC)

More questions about project banner

• All the mathematics field pages (e.g. Wikipedia:WikiProject Mathematics/Wikipedia 1.0/Number theory) are marked historical since 2012. Should they be removed from the template?
• The most frequently viewed articles are based on a list compiled in 2009. Can this be updated or should be field be removed?
• The A-class rating page is marked historical since 2015. Should this parameter also be removed?

— Martin (MSGJ · talk) 22:44, 27 October 2020 (UTC)

I have removed these features from the template now — Martin (MSGJ · talk) 15:41, 29 October 2020 (UTC)

I think it is nice to have "frequently viewed" in the banner itself. It has the subtle psychological impact that, when you see it on the talk page, it reminds you that school-students and home-makers are reading the article, and you should shift perspective and tone appropriately. In contrast to, say, DF-space, which is a safe space to geek out. 67.198.37.16 (talk) 18:35, 5 November 2020 (UTC)

Yes, it would be nice if we had any confidence in the reliability of the data ... Unless there is a more up-to-date list I don't think we should use the list from 2009 — Martin (MSGJ · talk) 20:34, 5 November 2020 (UTC)

Field no longer showing

The current banner no longer displays the field, which seems awkward. Will it be restored? Also, I'm not sure I like the multi-field proposal {{maths rating|algebra=yes|geometry=yes}} above; math being what it is, most articles will end up within half a dozen different fields. 67.198.37.16 (talk) 18:24, 5 November 2020 (UTC)

I removed them because, as noted above, the corresponding project pages have been marked historical for the last 8 years. However the data is not lost and the field can be restored again if the project wishes. (But we should probably unmark them as historical in that case.) — Martin (MSGJ · talk) 20:37, 5 November 2020 (UTC)

Category:Lists of mathematics articles

I have been trying to do some tidying in Category:WikiProject Mathematics and moving things to subcategories. One of these subcategories is Category:Lists of mathematics articles which I populated with Wikipedia:WikiProject Mathematics/List of mathematics articles (A) through Wikipedia:WikiProject Mathematics/List of mathematics articles (Z). Unfortunately I keep getting reverted by Mathbot, and its operator Oleg Alexandrov has suggested that I post here. Does anyone have any objections to this categorisation or suggestions for better names? — Martin (MSGJ · talk) 12:48, 19 October 2020 (UTC)

Articles that aren't in the mainspace shouldn't be in categories that look like they are intended for mainspace. That's my only comment on the matter. Category:WikiProject Mathematics lists would be fine. Otherwise, I agree they should probably be moved. --Izno (talk) 14:40, 19 October 2020 (UTC)

As it stands Category:WikiProject_Mathematics is rather dominated by the various lists of articles, so i support using a sub category, but it need to named it indicate project space. I would suggest Category:WikiProject Mathematics, list of mathematics articles.

There also seems to be some dead pages Wikipedia:WikiProject Mathematics/List of mathematics articles (A–C) has not been changed since 2013, so is presumably very out of date.--Salix alba (talk): 17:38, 19 October 2020 (UTC)

Okay fine Salix. But the comma looks strange so how about Category:WikiProject Mathematics list of mathematics articles or more succinctly Category:WikiProject Mathematics list of articles? The A-C page just transcludes the three separate pages A, B and C. Don't know why it's needed — Martin (MSGJ · talk) 18:22, 19 October 2020 (UTC)

Happy with Izno's suggestion also — Martin (MSGJ · talk) 18:23, 19 October 2020 (UTC)

I've marked the category with a temporary {{emptycat}} tag so it won't be continually tagged for CSD C1...please remove the tag when a decision has been made. Thanks. Liz ^{Read! Talk!} 14:37, 20 October 2020 (UTC)

Okay — Martin (MSGJ · talk) 17:16, 20 October 2020 (UTC)

Aren't lists such as List of mathematicians (A) mainspace lists? Why would they be categorized in Category:WikiProject Mathematics list of articles but not in any mainspace categories? Thanks. Starcheerspeaksnewslostwars^{Talk to me} 23:44, 23 October 2020 (UTC)

I think they should all be moved into project space because they are maintained by a bot. If a human makes a change, they will be likely be reverted by the bot in the next day. So I propose we move them all to Wikipedia:WikiProject Mathematics/List of mathematicians (A), etc. — Martin (MSGJ · talk) 18:51, 25 October 2020 (UTC)

Unless anyone has any comments on this, I will start moving them to project space shortly — Martin (MSGJ · talk) 13:12, 28 October 2020 (UTC)

Just to follow-up. These pages have all now been moved into project space and can be found in Category:WikiProject Mathematics list of mathematicians — Martin (MSGJ · talk) 22:42, 7 November 2020 (UTC)

US presidential election and edit warring at Benford's law

Not surprisingly, there has been considerable recent activity and edit warring at Benford's law with regard to its applicability to election fraud. The article would benefit from attention by knowledgeable editors. Paul August ☎ 10:05, 9 November 2020 (UTC)

Not surprisingly !! It seems the page has been protected, which should help. Frankly, that whole section relies much too heavily on primary sources. —JBL (talk) 13:05, 9 November 2020 (UTC)

I won't be touching that subsection of the page after what was added to it last week, since I now have a major COI with it (Walter Mebane is my PhD dissertation committee chair), but if anyone would like suggestions on sources please feel free to ping me into any relevant discussions. - Astrophobe (talk) 19:26, 9 November 2020 (UTC)

Punctuation

I found the first example below in an actual article. I changed it to the third.

Note also the second. It seems not universally realized that one of the differences between the system used here and full-fledged LaTeX is that a comma or period after a mathematical expression often gets misaligned or fails to match the font felicitously if it is outside rather than inside the math tags.

But I wonder whether there is someone who thinks either the first or the second form used here should be used. I keep seeing it and wondering whether people who do things like that when they're walking around bump into a telephone pole and suffer injuries. But that might not be the case if for some reason someone thinks it should be done that way.

First example:

$S(X,Y)={\begin{cases}1,&{\text{if }}Y<X\\{\tfrac {1}{2}},&{\text{if }}Y=X\\0,&{\text{if }}Y>X\end{cases}}$.

Second example:

$S(X,Y)={\begin{cases}1,&{\text{if }}Y<X\\{\tfrac {1}{2}},&{\text{if }}Y=X\\0,&{\text{if }}Y>X\end{cases}}.$

Third example:

$S(X,Y)={\begin{cases}1,&{\text{if }}Y<X,\\{\tfrac {1}{2}},&{\text{if }}Y=X,\\0,&{\text{if }}Y>X.\end{cases}}$

Michael Hardy (talk) 19:54, 8 November 2020 (UTC)

Surprisingly enough, I have just written the item Single brace in List of mathematical symbols. I have omitted the final period for being sure that nobody will think that this is a part of the notation. I have omitted also the commas at the end of the lines, because, without the final period they would be strange. I have also omitted the commas before the "if"s, but I am not sure whether there are needed or not. So, other editors opinions would also be useful for me.

In Michael's case, if final punctuation is required, it is clearly the third example that is the best. However, in many case, I would prefer to avoid punctuation at the end of lines, for example by having a colon that precedes the displayed formula ("we have thus:"). D.Lazard (talk) 21:06, 8 November 2020 (UTC)

I have changed my opinion: The third example is semantically incorrect: For the English syntax, a formula must be treated as a single entity. In these examples, the different cases belong to the same formula, as shown by the equal sign before the brace. Using end-line commas is thus similar to add a comma at the end of each row of a matrix. The absence of a right bracket does not make any semantic difference. So only the first two examples are semantically correct, and the second one provides a better rendering. However this looks strange, and omitting the period should be preferred, although, for purists, this may need to change the formulation for having a formula that is not a part of a complete sentence. This allows to apply MOS:LISTFORMAT: "A list item should not end with a full stop unless it consists of a complete sentence or is the end of a list that forms one." After all, for html semantics, a displayed formula is a list reduced to a single item. D.Lazard (talk) 13:41, 9 November 2020 (UTC)

It was my understanding that one places the punctuation mark at the end of the final item on the list, if one is treating the single brace expression as a single grammatical entity. That is, something like

$S(X,Y)={\begin{cases}1,&{\text{if }}Y<X\\{\tfrac {1}{2}},&{\text{if }}Y=X\\0,&{\text{if }}Y>X.\end{cases}}$

This is the main way I have seen it punctuated. It looks much less nasty than having the full stop in the middle of the expression vertically.Tazerenix (talk) 17:50, 9 November 2020 (UTC)

For what it's worth, I tend to agree. As someone who normally feels semantically giddy or syntactically bereft through a lack of expected punctuation, I much prefer this fourth example. It makes sense to apply English language punctuation to the entity as a whole. And to consider if less is more. Punctuation functions as a necessary disambiguator where text is linear; when the maths is 2D, it can be the spacing, row ends, etc, that helps with the parsing. I spent an embarrassingly long time trying to figure out if my screen was dirty when I first saw Examples 1 and 2. NeilOnWiki (talk) 18:34, 9 November 2020 (UTC)

I also agree with Tazerenix. —David Eppstein (talk) 19:01, 9 November 2020 (UTC)

Ok, Tazerenix's version make sense. D.Lazard (talk) 20:08, 9 November 2020 (UTC)

Listing proper units in a template

 You are invited to join the discussion at Template talk:Canadian election result § Template-protected edit request on 10 November 2020. Joeyconnick (talk) 06:58, 14 November 2020 (UTC)

Missing LaTeX macros: mathstrut, vphantom, vrule, and smash

Wikipedia's lobotomized version of LaTeX doesn't include mathstrut, vphantom, vrule, or smash. Does anyone know how to persuade it to make ${\sqrt {a^{2}+b^{2}}}$ and ${\sqrt {(a+r)^{2}+b^{2}}}$ have square roots the same size as each other? All the answers I can find on the web for this use one of these four missing macros. —David Eppstein (talk) 06:27, 13 November 2020 (UTC)

Calling it a "version of LaTeX" makes me uncomfortable. Genuine LaTeX does immensely more than typest mathematical notation. I wonder if those who master the software used here, and who see everyone call it "LaTeX", will think they've learned LaTeX and then go into shock when they encounter actual LaTeX and find they have no idea how to use it. E.g. what's this "\begin{document}" and "\usepackage" and "\setcounter{enumi}{6}" and "\input{ch6.tex}" and "\section*{blahblah}", etc? Michael Hardy (talk) 18:17, 16 November 2020 (UTC)

These two look the same size: ${\sqrt {(a^{2})+b^{2}}}$ and ${\sqrt {(a+r)^{2}+b^{2}}}$, but I suspect this may not be the answer you were looking for. --{{u|Mark viking}} {Talk} 23:02, 16 November 2020 (UTC)

I found a really really gross hack that appears to work: ${\sqrt {a^{2}+b^{2}{}_{\!}}}$ and ${\sqrt {(a+r)^{2}+b^{2}}}$. —David Eppstein (talk) 23:15, 16 November 2020 (UTC)

I was thinking along similar hack-y lines, like overset-ing a blank space on both: ${\sqrt {\overset {\,}{a^{2}+b^{2}}}}$ versus ${\sqrt {\overset {\,}{(a+r)^{2}+b^{2}}}}$. Yours seems more successful. XOR'easter (talk) 23:18, 16 November 2020 (UTC)

What is the use case for this? --JBL (talk) 00:22, 17 November 2020 (UTC)

Sometimes display=inline can help: ${\textstyle {\sqrt {a^{2}+b^{2}}}}$ and ${\textstyle {\sqrt {(a+r)^{2}+b^{2}}}}$ –jacobolus (t) 08:42, 22 September 2021 (UTC)

Covariance Matrix in Principle Component Analysis

Hello all,

In Principle Component Analysis, $X^{\top }{}X$ is stated to be proportional to the covariance matrix without proof or source. I believe it would be helpful to show how $X^{\top }{}X$ is related to the covariance matrix. Would adding the detail on how it is derived run afoul of WP:OR? -Mys_721tx (talk) 18:41, 17 November 2020 (UTC)

Scientific articles such as this have broad leeway in showing such details. See for example Wikipedia:CALC. So go ahead. That said, the proof maybe should not be included if it is long and pedagogical. See for example Wikipedia:TEXTBOOK. Mgnbar (talk) 18:59, 17 November 2020 (UTC)

The article on PCA seems a little light on in-line references as it is. Perhaps the first thing to do is find a textbook with an explanation that you particularly like and add a citation to it. And, as Mgnbar pointed out, Wikipedia articles aren't really the place for stepping through derivations one equation at a time; it's more important to say what a result is, what it implies, and what goes into proving it. There aren't hard-and-fast rules about this, however. XOR'easter (talk) 19:07, 17 November 2020 (UTC)

Thanks all! I cited Jolliffe 2002 and also fixed some other references in the same book. -Mys_721tx (talk) 19:57, 17 November 2020 (UTC)

RfC on the selectiveness of AMS fellowships

Hi all, I started a RfC Wikipedia talk:WikiProject Biography#RfC on AMS fellowship selectiveness to help determine if the American Mathematical Society fellowships count as selective enough to qualify mathematicians as notable under WP:NACADEMIC. If you know of consensus that has already been reached on this and believe I should withdraw the request, please let me know. I searched through the archives and could not find a past discussion on the topic, though I may have missed something. Thanks! Footlessmouse (talk) 23:38, 21 November 2020 (UTC)

Notation/formatting at Grassmannian

Anyone who enjoys arguing about mathematical notation and formatting is invited to weigh in here. --JBL (talk) 20:37, 22 November 2020 (UTC)

Cool commutative diagram builder app

Hey all,

I ran into this really cool commutative diagram building app today called quiver. And wow, it works really well. I'm surprised how easy it was to draw out a 3-commutative diagram using latex and their graphical editor. This is by far one of the most powerful tools (besides a latex compiler) for building diagrams. Unfortunately, it doesn't look like the app can export to SVG as of now, but it is on the list of github issues. Hopefully some other people here will find this tool useful :) . Wundzer (talk) 20:09, 25 November 2020 (UTC)