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Are Wikipedia's mathematics articles targeted at professional mathematicians?
No, we target our articles at an appropriate audience. Usually this is an interested layman. However, this is not always possible. Some advanced topics require substantial mathematical background to understand. This is no different from other specialized fields such as law and medical science. If you believe that an article is too advanced, please leave a detailed comment on the article's talk page. If you understand the article and believe you can make it simpler, you are also welcome to improve it, in the framework of the BOLD, revert, discuss cycle.
Why is it so difficult to learn mathematics from Wikipedia articles?
Wikipedia is an encyclopedia, not a textbook. Wikipedia articles are not supposed to be pedagogic treatments of their topics. Readers who are interested in learning a subject should consult a textbook listed in the article's references. If the article does not have references, ask for some on the article's talk page or at Wikipedia:Reference desk/Mathematics. Wikipedia's sister projects Wikibooks which hosts textbooks, and Wikiversity which hosts collaborative learning projects, may be additional resources to consider.
See also: Using Wikipedia for mathematics self-study Why are Wikipedia mathematics articles so abstract?
Abstraction is a fundamental part of mathematics. Even the concept of a number is an abstraction. Comprehensive articles may be forced to use abstract language because that language is the only language available to give a correct and thorough description of their topic. Because of this, some parts of some articles may not be accessible to readers without a lot of mathematical background. If you believe that an article is overly abstract, then please leave a detailed comment on the talk page. If you can provide a more down-to-earth exposition, then you are welcome to add that to the article.
Why don't Wikipedia's mathematics articles define or link all of the terms they use?
Sometimes editors leave out definitions or links that they believe will distract the reader. If you believe that a mathematics article would be more clear with an additional definition or link, please add to the article. If you are not able to do so yourself, ask for assistance on the article's talk page.
Why don't many mathematics articles start with a definition?
We try to make mathematics articles as accessible to the largest likely audience as possible. In order to achieve this, often an intuitive explanation of something precedes a rigorous definition. The first few paragraphs of an article (called the lead) are supposed to provide an accessible summary of the article appropriate to the target audience. Depending on the target audience, it may or may not be appropriate to include any formal details in the lead, and these are often put into a dedicated section of the article. If you believe that the article would benefit from having more formal details in the lead, please add them or discuss the matter on the article's talk page.
Why don't mathematics articles include lists of prerequisites?
A well-written article should establish its context well enough that it does not need a separate list of prerequisites. Furthermore, directly addressing the reader breaks Wikipedia's encyclopedic tone. If you are unable to determine an article's context and prerequisites, please ask for help on the talk page.
Why are Wikipedia's mathematics articles so hard to read?
We strive to make our articles comprehensive, technically correct and easy to read. Sometimes it is difficult to achieve all three. If you have trouble understanding an article, please post a specific question on the article's talk page.
Why don't math pages rely more on helpful YouTube videos and media coverage of mathematical issues?
Mathematical content of YouTube videos is often unreliable (though some may be useful for pedagogical purposes rather than as references). Media reports are typically sensationalistic. This is why they are generally avoided.
Why is wikipedia lagging behind the rest of the world in not creating an article on τ (2π)?
The notability of τ=2π is not yet established. Neither the mathematics community nor the math education community has responded to the proposed new constant in any notable way. τ=2π does not at this point of time meet the criteria of notability as per Notability or Wikipedia:Notability (numbers)
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How can I join?
Please join me here. :) — Preceding unsigned comment added by Sophie Concepcion (talk • contribs) 11:36, 16 May 2015 (UTC)
Tapering (mathematics)
Deletion of Tapering (mathematics) has been proposed. Is the article worth keeping? Michael Hardy (talk) 14:24, 4 May 2015 (UTC)
- The article is indeed rather unclear in its current form, but tapering is certainly an important concept. However, it is covered in Window function. FireflySixtySeven (talk) 22:33, 4 May 2015 (UTC)
- Tapering is well-known operation in solid modeling in computer graphics. It is a shape deformation operation, like bending or twisting [1], that alters the mesh representing solid, often deforming part of the shape down into a conical or prism-like section.. It is more akin to the tapering one does in a machine shop than tapers used in, for instance, signal processing. Definitely has nothing to do with exponential decay. I'm going to deprod, but a move to Tapering (computer graphics) may be warranted. --Mark viking (talk) 23:37, 4 May 2015 (UTC)
Platonic solid - Classification
Please offer a view at Platonic solid#Classification. The issue concerns whether the existence of the five Platonic solids can be answered easily by an explicit construction, or cannot. Johnuniq (talk) 06:53, 5 May 2015 (UTC)
- As for me, yes, it can (easily or not - this may be controversial). Boris Tsirelson (talk) 10:29, 5 May 2015 (UTC)
- Agreed, "cannot" makes no sense here. --JBL (talk) 15:31, 5 May 2015 (UTC)
- Likewise. I have corrected the statement. —Mark Dominus (talk) 15:00, 7 May 2015 (UTC)
Watch out for crank user 108.242.169.13
108.242.169.13 (talk · contribs) came to my attention because of these edits to Talk:Van_der_Waerden_number; the author claims to have solved the (open) problem of the minimal n such that any k-coloring of the integers 1…n must contain a monochromatic k-term arithmetic progression. Since Wikipedia policy restricts talk page discussions to discussions about the article, this revelation was removed, once by mfb (talk · contribs) and once by myself. I also posted a relevant admonishment on 108.242.169.13's talk page. He is irate, and perhaps a response is in order. I tried to write one, but it came out unacceptably rude so I am not going to post it. The best response may be no response at all, just remove his material without engaging him.
The user claims to be Bill Bouris, a high school and community-college teacher of mathematics; his web site http://www.oddperfectnumbers.com/ is filled with similar crankery, boasting many unintelligible solutions of longstanding open problems. For example, he claims to have proved that there are no odd perfect numbers. He has also begun discussions on similar crankery at at least four other pages, which you can see in his user contributions page. mfb (talk · contribs) has reverted most of it, except at Talk:Langford_pairing, where David Eppstein (talk · contribs) opted to bring it back. —Mark Dominus (talk) 23:03, 6 May 2015 (UTC)
He has also appeared as 99.135.160.136 (talk · contribs). —Mark Dominus (talk) 23:06, 6 May 2015 (UTC)
- We can remove again from the Langford pairing talk if you prefer. I brought it back only because it was a removal of talk page content without an adequate edit-summary explanation for what was being removed and why, if I remember correctly. I agree that it's crankery and is unlikely to be usable to improve the encyclopedia. —David Eppstein (talk) 23:21, 6 May 2015 (UTC)
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- I have no preference either way, and I did not mean to criticize your action, only to report on the current status. —Mark Dominus (talk) 23:30, 6 May 2015 (UTC)
PigTex
Is this just my lack of understanding of Tex?
Below, the "A" and "B" are supposed to be absent.
Remove "A" to obtain
Remove "B" (but keep "A"), then (Removed crashing Tex to save eyes)
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(Using PNG) YohanN7 (talk) 13:52, 7 May 2015 (UTC) Interestingly, MathML gives a more informative error message:
- Failed to parse (Conversion error. Server ("http://mathoid.svc.eqiad.wmnet:10042") reported: "Error:["TeX parse error: Bracket argument to \\\\ must be a dimension"]"): {\begin{aligned}A[G_{m}^{i},G_{n}^{j}]&={C^Template:Ij}_{k}G_Template:M+n^{k}+\delta _{m}^Template:Ij\delta _Template:M+n,0C\\[C,G_{m}^{i}]&=0.\end{aligned}}
This is different from what PNG reports. YohanN7 (talk) 13:59, 7 May 2015 (UTC)
Solution?
Insert some air in the form of a pair of braces {}, "A" -> "{}", "B" -> "{}":
Both pairs of braces are necessary. I guess this is due to my lack of understanding of Tex. The square brackets are usually used to pass additional arguments to an "environment", right? YohanN7 (talk) 14:08, 7 May 2015 (UTC)
- Presumably the problem is with how the parser treats the \begin{align}. It looks to me like it is expecting an optional argument (which would be enclosed in square brackets). I don't think align accepts any arguments in LaTeX, so this must be something specific to our implementation. Sławomir Biały (talk) 14:41, 7 May 2015 (UTC)
- A bracket that follows immediately a Latex command is generally considered as an optional parameter to this command, even if this command does not accept any optional parameter. In the case of "\begin", which does not has any optional argument, this optional argument is simply ignored (it is possible that some parsers consider the [ as a part of the text, but this is clearly not the case, here). In the case of "\\", the optional argument, if present, indicates the size of the vertical space. Therefore, the error signal is correct, as well as the suggested correction. D.Lazard (talk) 15:24, 7 May 2015 (UTC)
- Thanks. YohanN7 (talk) 15:44, 7 May 2015 (UTC)
- But if the command has no optional parameters, latex interprets brackets as ordinary brackets. The above commands all work as intended in ordinary latex. This is not what appears to be happening here. Sławomir Biały (talk) 16:30, 7 May 2015 (UTC)
- A bracket that follows immediately a Latex command is generally considered as an optional parameter to this command, even if this command does not accept any optional parameter. In the case of "\begin", which does not has any optional argument, this optional argument is simply ignored (it is possible that some parsers consider the [ as a part of the text, but this is clearly not the case, here). In the case of "\\", the optional argument, if present, indicates the size of the vertical space. Therefore, the error signal is correct, as well as the suggested correction. D.Lazard (talk) 15:24, 7 May 2015 (UTC)
Stella (software)
Can anyone more familiar with our guidelines on software determine if Stella (software) is notable? I can't escape the feeling that Wikipedia is being used as a marketing platform here. Sławomir Biały (talk) 13:10, 8 May 2015 (UTC)
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I personally not familiar with Stella, but I know that scientists use Stelle to model natural enviroments
[http://www.uvm.edu/~jphoffma/GSA/Generic.pdf Dr. E. Alan Cassell,Short Course System Dynamics Modeling of Natural Environments: An Introduction to STELLA Sunday 11 March 2001 Geological Society of America Northeastern Section 36th Annual Meeting, So. Burlington, VT.]
- [ https://books.google.ca/books?id=e6PaBwAAQBAJ&pg=PA41&dq=Stella+modelling&hl=en&sa=X&ei=i1xOVYmEJY6fyATKuoDQCQ&ved=0CFMQ6AEwCA#v=onepage&q=Stella%20modelling&f=false simulation of economic]
- I don't go by "feeling" to judge an article. It is extremely irresponsible hooliganism--Gisling (talk) 19:22, 9 May 2015 (UTC).
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- Note to Gisling: the STELLA simulation software that you mention is not the same as the Stella polyhedron modeling software discussed in Stella (software). I agree that the STELLA simulation software is likely notable--at least I have seen a number of reviews, and as you note, books. But other than passing mentions at Geometry Junkyard and in a book, I've been unable to find secondary reviews of the Stella polyhedron software that are reliable. Probably not notable. --Mark viking (talk) 19:34, 9 May 2015 (UTC)
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- Well, given that the best you could come up with is a completely different software, I take it you agree that this is non-notable WP:ADVERTISING. And, fwiw, compliance with WP:NOT is not "hooliganism". That's just a baseless personal attack, which looks particularly silly given that you apparently failed to understand what the article was about. Sławomir Biały (talk) 21:06, 9 May 2015 (UTC)
- I have Stella software, and I've used it for making many of the polyhedron images on Wikipedia. But on notability standards, I'm not in a position to offer an opinion. Tom Ruen (talk) 02:55, 13 May 2015 (UTC)
It is now at AfD: Wikipedia:Articles for deletion/Stella (software). Sławomir Biały (talk) 13:07, 16 May 2015 (UTC)
Articles by Gisling
I would like to solicit opinions on how to handle the numerous articles by Gisling which consist largely of Maple 16 calculations and graphs. On his talk page several editors have raised concerns about these articles. In some cases, such as at Eckhaus equation, an editor went over the article, corrected it, and produced something respectable. In other cases, such as at Fujita-Storm equation, the concerns were not addressed. I started a discussion at Wikipedia:Articles for deletion/Bogoyavlenski-Konoplechenko equation asking to delete an article (and probably some related articles) on the flimsy grounds of WP:TNT in cases where I can't determine if even the subject of the article is accurately described (as it was not at Eckhaus equation - even the definition of this equation was erroneous.) I gutted several articles last night, but stopped short of going over all of them as I expected some resistance (which did occur this morning.) Note that Gisling has also contributed a large amount of quality material on the history of Chinese mathematics and other topics. --Sammy1339 (talk) 16:01, 9 May 2015 (UTC)
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- Majority of nonlinear differential equation and special function articles are sourced from US Government source:
United States Government: National Institude of Standards and Technolgy, Handbook of Mathematical Functions, Cambridge University Press 2010 printed edtion, 950 pages.( I bought this printed book)
there is also a web edition
US Government NIST Handbook of Mathematical Functions, full of color diagrams of various mathematical functions
It is a common practice in mathematics to plot graphs using either Matlab,Mathematica or Maple, for instance the graphs in Mathworld is generated wityMathematica, if you don't know how to make graphs using one of these, you have poor qualification , you are not qualified to edit any mathematic articles on wikipedia --Gisling (talk) 18:09, 9 May 2015 (UTC)
- I don't think anyone objects to a few carefully selected plots that illustrate things well, but we shouldn't add plots just for their own sake. This is especially true of animations, which should be selected very carefully (see WP:IUP#ANIM) because of their generally larger file size, the inability to print or display on different media, as well as the fact that most readers find animations distracting. None of the animations in question seem to be good illustrations suited for the articles that they inhabit. Some samples are the galleries at: Discrete_q-Hermite_polynomials, q-Charlier_polynomials, Little_q-Laguerre_polynomials, q-Hahn_polynomials, Discrete q-Hermite polynomials, Continuous q-Jacobi polynomials, Continuous q-Laguerre polynomials, Affine q-Krawtchouk polynomials, Little q-Jacobi polynomials, dual q-Hahn polynomials, Al-Salam–Chihara polynomials, q-Racah polynomials. Even the stills at Coshc_function show poor judgement in the scale of the coordinate plane. (Who the hell plots a hyperbolic function over a domain like [-10,10]??) Clearly, your own advice is relevant: "if you don't know how to make graphs using one of these, you have poor qualification , you are not qualified to edit any mathematic articles on wikipedia". So, in short, I agree with the original poster that these galleries are a problem and many of them (including all of the animations) should be removed entirely per our image use guidelines.
- Also, there is 唐戈 (talk · contribs · deleted contribs · logs · edit filter log · block user · block log), who seems to be stalking this issue and reverting any attempt to remove the galleries, otherwise defending Gisling's contributions at AfD, and inserting similar lists of unreferenced, poorly-formatted formulas into articles. I strongly get the impression that this is a sockpuppet or meatpuppet. Sławomir Biały (talk) 19:30, 9 May 2015 (UTC)
- This talk page interaction is pretty discouraging, though I guess the final outcome was right. I agree that the animations I've seen on the pages linked in this discussion are useless. --JBL (talk) 21:45, 9 May 2015 (UTC)
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- Comment" I don't think this gentleman [2] is qualified to judge animations, because he never did one. Don't listen to what he talk, see what he did: he contributed only very simple 2D graphs in wikicommons, I don't think he has the ability to make 3D graphs in complex space, let alone animation.
Why animation ? When you have a function with more then 3 variables, the simplest way to visualize is make one parameter changes, then make animation plots. Apparently, this gentleman never makes a single graph with more than three variable
Any comparision ?? [3]
--Gisling (talk) 00:00, 10 May 2015 (UTC).
- There are several fallacies here that need pointing out. First of all, the ability to create animations is not necessary to judge their suitability for an article. Secondly, as I have said, Wikipedia articles generally use animations very sparingly. So as a rule, I generally do not upload animations. But, thirdly, your entire methodology is flawed. I have uploaded animations, of a substantially higher quality than any of yours by the way. (I think the link you kindly provided above to your long list of bad, jerky, animations, with poorly selected aspect ratio, coloring, and mesh underscores this point. Any mathematical content of conceivable encyclopedic value in these animations is lost just from the sheer ugliness of this animatory effluent.) Sławomir Biały (talk) 01:07, 10 May 2015 (UTC)
Incidentally: the user whose username consists of two characters has been blocked indefinitely while Gisling has been blocked for three days for sock puppetry. --JBL (talk) 01:34, 10 May 2015 (UTC)
The quality of the TeX code at Fujita–Storm equation is still deficient, but far better than it was originally. If Gisling would improve his or her TeX skills, that would be a step in the right direction. For example:
should be changed to
etc. Michael Hardy (talk) 21:30, 12 May 2015 (UTC)
Pearcey Integral graphs
US Government National Institude of Standard and Technology:NIST Handbook of Mathematica Functions has nice graphs of Pearcey Integral
Can some one who claimed to be "Mathematica expert" provides similar graphs ?, Othewise, remove "Mathematica expert" claim please--Gisling (talk) 22:59, 9 May 2015 (UTC).
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- Aren't these images public domain anyway, if they are published by the US Government? Why reinvent the wheel? Sławomir Biały (talk) 23:48, 9 May 2015 (UTC)
- If the federal government is the author of the work, as would be the case if the work were made for hire by its employees while on the job, then it is not subject to copyright. But the fact that the federal government publishes it, i.e. distributes it to the public, is not exactly the same thing. The federal government can buy a copyright or acquire it by bequest or donation, etc., and publish the work, and it's subject to copyright. Michael Hardy (talk) 21:07, 12 May 2015 (UTC)
- Aren't these images public domain anyway, if they are published by the US Government? Why reinvent the wheel? Sławomir Biały (talk) 23:48, 9 May 2015 (UTC)
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- Yes, I see http://dlmf.nist.gov/about/notices does not allow commercial re-use. Sławomir Biały (talk) 21:48, 12 May 2015 (UTC)
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- Not that simple, you need to explain how that graph is obtained, I cannot just copy it and paste it to wikicommons, without knowing why and how. Honestly, I don't know how these plots were obtained(I never claimed myself as Maple expert), may be you can, Mathematica expert ? How about give it a try please, it is not that simple--Gisling (talk) 00:09, 10 May 2015 (UTC).
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- I am willing to make suggestions if you actually show a genuine interest, but I'm not getting that feeling from the interactions with you thus far. Instead, you have described me in the above thread as a "hooligan", in the AfD as "bloody ignorant", and this very thread seems like trolling in an overt attempt to bait me. (Why you have chosen to single me out, I do not know.) If you are genuinely interested in working it out, please post a comment over at the reference desk (this is not the right forum for such questions), including any details you think might be relevant to the computation, and I'll gladly see what I can do. Sławomir Biały (talk) 00:50, 10 May 2015 (UTC)
Full rank
My colleagues and I agree that the property of being "full rank" makes perfect sense and has a conventional definition for rectangular matrices. However, none of the books I have on hand give a definition. Can anyone produce a RS? (Refer: [4].) --JBL (talk) 00:50, 13 May 2015 (UTC)
- The book by Gentle on Matrix Algebra, section 3.36, discusses the notion of full rank for non-rectangular matrices. --Mark viking (talk) 02:58, 13 May 2015 (UTC)
- That book refers to a "full [hyphen omitted] rank matrix" rather than to a full-rank matrix. Punctuation was taught in elementary school when I was there; the reason why one should write about a "full-rank matrix", with a hyphen, and also say that a matrix "is of full rank", without a hyphen, is quite simple, and the presence or absence of the hyphen can effectively convey a lot of information in some cases (e.g. the difference between a "man-eating shark", which scares people away from beaches, and a "man eating shark", who is a customer in an exotic restaurant). I think people are still accustomed to seeing the traditional standard use of hyphens in magazines, newspapers, and books on subjects in which the non-technically-trained copy-editor is not afraid to say too much, although writers of advertising copy and package labeling do not use it. I think maybe it could still be saved, if an effort were made. Michael Hardy (talk) 17:52, 14 May 2015 (UTC)
@Mark viking :
- What do you mean by a "non-rectangular matrix"?
- Does that book anywhere give an explicit definition of "full rank" for matrices that are not square?
BTW, there's a pretty bad typo in equation (3.122) in that book. It says
where it should say this:
Michael Hardy (talk) 18:11, 14 May 2015 (UTC)
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- Ah sorry, that was a typo (or perhaps a thinko). I meant to say non-square.
- On page 77, last paragraph, the books says if the rank of a matrix is the same as its smaller dimension, then the matrix is of full rank. Then it goes on to note that "full row rank" and "full column rank" are typically used when discussing non-square matrices. No hyphens in any of these definitions in the book as far as I can tell. --Mark viking (talk) 20:02, 14 May 2015 (UTC)
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- Our article Rank (linear algebra) seems a little confused on whether a matrix having full rank is (a) both of full column rank and full row rank (and hence a square matrix), or (b) either of full column rank or full row rank (and hence can be non-square). I find the second repugnant – it seems like what would be used when someone is too lazy to use the term full column rank or full row rank as appropriate. What is the dominant use? (I already put in a note, but no-one of knowledge has chipped in.) —Quondum 00:41, 15 May 2015 (UTC)
Over a field, a square matrix is invertible if and only if it is full-rank (right?) So, I don't think "full-rank" is particularly useful for a square marrix. For a non-square matrix, a "full-rank", I think, has the usual meaning, meaning the rank (row rank) is the maximal possible; i.e., the matrix defines a surjection when it is viewed as a linear transformation. For example, to check the submersion theorem applies one checks if the Jacobian matrix has full-rank, meaning it is surjective; see for instance [5]. At least, this (full-rank = surjective) is how I use the term in my day life. -- Taku (talk) 19:41, 15 May 2015 (UTC)
- I don't feel that just because in some instances another definition happens to be equivalent that one should consider one of them "not particularly useful". Your argument of being equivalent to being surjective is far more persuasive. (Your first argument would argue against using a new term for 'surjective', though!) In the context of matrices, one cannot call a matrix 'surjective' though: it is left-multiplication by that matrix which would be surjective, or right-multiplication my that matrix. So again, one is looking at calling it 'full row rank' or 'full column rank', with 'full rank' being only sensible where the two are equivalent (e.g. square matrices over a field). —Quondum 20:24, 15 May 2015 (UTC)
- Full-rank ⇔ surjective is just not right. But I have never seen 'full row rank' or 'full column rank'. 'Full rank' is unambiguous, but it may be more common to call it 'maximal rank', at least in differential geometry (it is still referring to matrices). YohanN7 (talk) 23:00, 15 May 2015 (UTC)
- The term 'maximal rank' makes much more sense than 'full rank' when this meaning is intended, and if it is more common, the article could be updated accordingly, subject to sourcing/dominance. —Quondum 01:04, 16 May 2015 (UTC)
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- Right or not, my point was using "full-rank" for "surjectivity" seems fairly common at lease in differential geometry. The reason I think is that it doesn't make sense to say whether a matrix is surjective or not; thus, "full-rank" becomes a shorthand for the linear transformation given as the left multiplication by the matrix being surjective (doesn't roll well on the tongue, does it?). For a square matrix, there is no need for the term "full-rank" (except in the pedagogical context) since "invertible matrix" is simpler and more precise. -- Taku (talk) 02:32, 16 May 2015 (UTC)
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- You need to be careful about the precise meaning: words used in mathematics are often used imprecisely, with a lot implied by context. For example, 'Jacobian matrix' may be used to refer to the matrix, but implied may be the mapping between tangent spaces that it represents, which implies 'left multiplication by'. This does not apply to matrices in general, where properties often are not referenced to the properties of the operators they might represent, but typically more directly in terms of the components of the matrix. So in matrices, my perception is that the rank seems to be mostly defined in terms of the dimension of the space spanned by the rows or columns, respectively. This is not the same thing as the dimension of the image of its left and right multiplication, or whether it is surjective, because these are determined by the dimension of the domain and the dimension of the codomain, which can be less or more respectively than the number of columns and rows. So the fit is really quite poor. —Quondum 03:19, 16 May 2015 (UTC)
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- There seems some confusion. By definition, I agree, the row/column rank is the dimension of the space spanned by rows/columns (they turn out to be the same number). But the rank of the matrix can be equally characterized by the dimension of the image of the linear transformation determined by a matrix. Via the use of a transpose, we only need to consider the case by the left multiplication. Then the rank of the matrix is the dimension of the image of the matrix viewed as a linear transformation. In other words, there might be some "a priori" distinction that can be made from matrix point of view and operator point of view, but the distinction is not too important to be concerned in practice. A case in point: one speaks of finite-rank operator (by the way, as Michael Hardy noted, the universe collapses if you forget hyphen here) even though it is not really a matrix. Taku (talk) 14:10, 17 May 2015 (UTC)
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- You seem to be missing what I'm saying. The rank of a vector space can be less than the dimension of its representation (it is equal to the size of the basis, and hence the rank of a map can be less than the rank of the matrix chosen to represent it). When defining the rank of a matrix, Bourbaki explicitly uses vector spaces of dimension equal to the dimensions of the matrix. Without this, your second statement in the above paragraph does not hold.
- Bourbaki covers the rank of both a linear map and of a matrix in detail, but does not mention the concept of maximal rank in any form. I'd posit that the concept of a maximal-rank matrix has little utility – little enough that I would trim the definition to an observation that when the terms maximal rank or full rank are used, these terms typically mean "[description here]". We have sufficient sources to make this diminished statement. —Quondum 00:25, 18 May 2015 (UTC)
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- It seems to me like you're extrapolating too heavily from your own experience. "Full rank" was immediately recognized and understood by my office mates; I wouldn't bat an eyelash seeing (or using) it in a research paper. And we have at least two RSs in this thread with definitions (thanks very much to those who found them!), while I doubt very strongly that anyone will produce a RS that deprecates the term in the way you suggest. --JBL (talk) 01:10, 18 May 2015 (UTC)
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- I think a suitable definition of maximal rank has become clear (and I suppose we can assume that 'full rank' is a synonym). But what do you make of four out of six RSs mentioned in this thread that cover matrix rank simply failing to mention it? Should we present it as though it is mainstream and significant as if every RS had mentioned it? I was hoping some consensus would emerge, but it seems to be slow in coming; the proposals I make are merely strawmen for consideration. —Quondum 03:32, 18 May 2015 (UTC)
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- Okay, never mind. I've tweaked the article in the direction of maximal or full rank being defined for nonsquare matrices. At least that gets rid of the internal inconsistency, and does not change the article much. I'm not going to belabour this any further. —Quondum 04:26, 18 May 2015 (UTC)
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In case you're still looking, I found a reliable source: David C. Lay, Linear Algebra and Its Applications, 1994, Addison-Wesley, p. 242, exercise 26: "In statistical theory, a common requirement is that a matrix be of full rank. That is, the rank should be as large as possible." [Italics are in the original.] Mgnbar (talk) 00:01, 16 May 2015 (UTC)
And by the way books by Kolman, Hoffman and Kunze, and Halmos don't seem to mention full rank. Mgnbar (talk) 00:04, 16 May 2015 (UTC)
- I suggest we define either of 'full rank' or 'maximal rank' and provide the other one in an or-clause. While 'full column rank' and 'full row rank' both make sense, they don't seem to appear in the literature. Both imply 'full rank' and 'full rank' implies one or the other (or both) of them (if they were defined) supported by the theorem that says row-rank = column-rank. Lee defines 'maximal rank' for an m × n or n × m-matrix, n > m as one having a m × m minor of rank m. YohanN7 (talk) 17:05, 16 May 2015 (UTC)
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- I would hope we make no definition without it being a fairly standard term. That was why I initially requested some input: some sources clearly define full rank as the maximal rank for the matrix size, but if that is a minority definition, I would prefer to see to noted as such. If most sources use a different term, or define it some other way, we should document it accordingly. So far, no-one seems to have done more than consider an isolated source or so. I we have a few highly notable secondary sources defining it (how widely accepted is Lee?), we could do as you say. —Quondum 23:12, 16 May 2015 (UTC)
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- Well, Lee is no Bourbaki, he defines things on the fly (and is therefore readable as opposed to Bourbaki). My point is that it doesn't matter very much, just take one "reputable" reference at random, use it for the def and provide the alternative term. It can't get very much wrong. Unfortunately, my own supply of books in linear algebra is limited. YohanN7 (talk) 14:58, 17 May 2015 (UTC)
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With a risk of complicating the discussion further, I would like to mention yet another point of view: "full-rank" = "maximal rank" = "generic-rank". Here, I'm using "generic" in the following way. Let X be the (vector) space of all matrices of some fixed size (possibly non-square). We view X as an (affine) algebraic variety (X is simply a vector space.) Then the matrices of maximal possible rank form an open subset with respect to Zariski topology (it is the complement of the vanishing locus of minors.) So, a matrix in a general position has maximal possible rank and that's the generic rank of a matrix. (Do I make sense?) By definition, a matrix is full-rank if it has generic rank or equivalently maximal possible rank. -- Taku (talk) 14:38, 17 May 2015 (UTC)
- This vaguely resembles an example in Lee's book. The set of m × n matrices with full rank is open in M(m, n) in the subspace topology, hence a submanifold. YohanN7 (talk) 14:58, 17 May 2015 (UTC)
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- It is correct that "full rank" = "maximal rank", when considering the set of all m × n matrices. But, in the case of the a differentiable mapping, it may occur that the Jacobian matrix is never full rank, that is "maximal rank" < "full rank". On the other hand, when "generic rank" is defined (that is in the context of algebraic geometry), it is true that "maximal rank" = "generic rank". As an example of a situation where the term "full rank" is useful, and probably widely used, is the following result: Given a set of polynomials that generate a prime ideal, the algebraic variety of their common zeros is a complete intersection if the Jacobian matrix is "full-rank" at, at least, one point of the variety. In this case, the singular points are exactly the points where the Jacobian matrix is not full-rank. D.Lazard (talk) 09:56, 18 May 2015 (UTC)
Inline Latex again
ee s Talk:Spectral theorem. YohanN7 (talk) 23:09, 14 May 2015 (UTC)
- I would have expected an objective answer and/or discussion on the article's talk page, as you were the one who told me to put that issue there…--*thing goes (talk) 23:26, 14 May 2015 (UTC)
KasparBot
A bot is running amok and adding a template called 'Authority control' to the bottom of pages. It generates links that make little sense. See e.g. This version of Topological group (at the bottom). Is this legitimate? (If it is I'd say its legitimate bs, therefore bs, hence should not be here or anywhere.) YohanN7 (talk) 19:32, 16 May 2015 (UTC)
I mean, what is a link to National Diet Library doing there? whatever this is isn't much better. YohanN7 (talk) 19:52, 16 May 2015 (UTC)
- Think of it as being like an interwiki link, except that instead of going to the German-language Wikipedia entry on the same topic it goes to the German National Library's entry on that topic. We've had these on biography for a while now, but this is the first I've seen of them being added to abstract topics. —David Eppstein (talk) 20:03, 16 May 2015 (UTC)
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- They sometimes link to pages in Japanese. Legitimate nonsense or not, it is nonsense. YohanN7 (talk) 20:12, 16 May 2015 (UTC)
- What language would you expect a catalog entry from a Japanese national library to be in? Reading authority control might or might not help clarify what's going on here. —David Eppstein (talk) 20:35, 16 May 2015 (UTC)
- Doesn't matter if there is an explanation buried somewhere. What is the purpose? How does this improve the articles? Has this diet library (as they call themselves) donated $1 000 000 to English Wikipedida? YohanN7 (talk) 20:51, 16 May 2015 (UTC)
- You don't understand the purpose of a link from an article to library information about the same topic? This seems obvious, at least in the abstract. --JBL (talk) 21:01, 16 May 2015 (UTC)
- How does these links help me? Do they offer a free course in Japanese? You are right I don't understand. If there are good places to link I link them (manually). YohanN7 (talk) 21:05, 16 May 2015 (UTC)
- Possibly you should consider the possibility that some people speak English and Japanese, even if you are not among them. -JBL (talk) 21:12, 16 May 2015 (UTC)
- That's no answer. How does it help me and the (few) others that don't speak Japanese and English (or Bemba)? YohanN7 (talk) 21:22, 16 May 2015 (UTC)
- In exactly the same way that interwiki links to Japanese versions of articles don't help you. They're useful information for a subset of our readers that doesn't include you. —David Eppstein (talk) 21:38, 16 May 2015 (UTC)
- That's no answer. How does it help me and the (few) others that don't speak Japanese and English (or Bemba)? YohanN7 (talk) 21:22, 16 May 2015 (UTC)
- Possibly you should consider the possibility that some people speak English and Japanese, even if you are not among them. -JBL (talk) 21:12, 16 May 2015 (UTC)
- How does these links help me? Do they offer a free course in Japanese? You are right I don't understand. If there are good places to link I link them (manually). YohanN7 (talk) 21:05, 16 May 2015 (UTC)
- You don't understand the purpose of a link from an article to library information about the same topic? This seems obvious, at least in the abstract. --JBL (talk) 21:01, 16 May 2015 (UTC)
- Doesn't matter if there is an explanation buried somewhere. What is the purpose? How does this improve the articles? Has this diet library (as they call themselves) donated $1 000 000 to English Wikipedida? YohanN7 (talk) 20:51, 16 May 2015 (UTC)
- What language would you expect a catalog entry from a Japanese national library to be in? Reading authority control might or might not help clarify what's going on here. —David Eppstein (talk) 20:35, 16 May 2015 (UTC)
- They sometimes link to pages in Japanese. Legitimate nonsense or not, it is nonsense. YohanN7 (talk) 20:12, 16 May 2015 (UTC)
- Just to provide some background, naming authority files provide a standard naming ontology for library catalogs and are good for semantic web stuff, too. An example is the Integrated Authority File from the German National library. Working toward a standard ontology is a good thing for topic cross referencing and is one of Wikidata's objectives, IIRC. The question I have is: why are we linking to the National Diet Library of Japan naming authority, when the Library of Congress naming authority, called LCNAF, seems just as good and would be more immediately useful to English speakers? --Mark viking (talk) 22:12, 16 May 2015 (UTC)
- I have no inside knowledge, but the {{authority control}} template is fairly agnostic about such choices, merely reporting what is available on the wikidata entry for the article. So my guess is either (1) someone took the effort to enter Japanese naming authority data on wikidata and nobody has done the same thing for LCNAF, or (2) someone took the effort to program the automatic transcription of Japanese authority control wikidata into our authority control template, and nobody has done the same thing for LCNAF. —David Eppstein (talk) 22:30, 16 May 2015 (UTC)
- That makes sense, thank you. --Mark viking (talk) 00:23, 17 May 2015 (UTC)
- I have no inside knowledge, but the {{authority control}} template is fairly agnostic about such choices, merely reporting what is available on the wikidata entry for the article. So my guess is either (1) someone took the effort to enter Japanese naming authority data on wikidata and nobody has done the same thing for LCNAF, or (2) someone took the effort to program the automatic transcription of Japanese authority control wikidata into our authority control template, and nobody has done the same thing for LCNAF. —David Eppstein (talk) 22:30, 16 May 2015 (UTC)
Since this occupies a box of height at least three lines, it could at least spell out what it is about and where the links go. E.g. NDL → National Diet Library. It is also inconsistent. Sometimes it links to, not a library wiki-entry but to Integrated Authority File. Instead of saying "Authority control" it should spell out what the hell it is supposed to be. "Library catalog entry" or whatever. A parenthetical (in Japanese) might be appropriate when applicable.
When I first encountered this, I clicked the links and immediately took it for vandalism/some sort of unauthorized promotion. YohanN7 (talk) 09:03, 17 May 2015 (UTC)
As it is now it is just amateurish littering (yes, I am now aware that there are people around speaking Japanese—even German—thanks all for patiently explaining this to me). While we are at it, there is also the LIBRIS authority file. That would serve Swedish-speakers well. YohanN7 (talk) 09:03, 17 May 2015 (UTC)
- "This metadata template links Wikipedia articles to various library catalogue systems. At the moment, it is used almost exclusively in biographical articles and on user pages." (Quoted from Template:Authority control.) Really? Boris Tsirelson (talk) 11:08, 17 May 2015 (UTC)
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- This is not true: It has been added to Graph theory, Real number, Integer, Number theory, Diophantine approximation, Division (mathematics), Numeral system, Binomial, Number, Angle, Equation, Arithmetic, Logarithm (this is the list of the articles of my watchlist to which the article has been added yesterday or today). D.Lazard (talk) 12:32, 17 May 2015 (UTC)
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- I raised the issue at Template talk:Authority control. Sławomir Biały (talk) 13:53, 17 May 2015 (UTC)
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The essay Wikipedia:Authority control has more information about this. It seems like authority control was first implemented on the German Wikipedia, and the template is now being propagated via the interwiki links. I don't know enough to say if this is a good idea. I think a legitimate concern is that, as far as I know, interwiki links are not very well validated. But that would seem to defeat the purpose of authority control. A more immediate concern though is that the template itself is very confusing to readers (as evidenced by the existence of this very thread). It is quite possible that a reader can see the template, click the link to the article Authority control, read that article, and still have no idea what the damn thing is about. This at least should be fixed, perhaps by replacing the link in the template to Wikipedia:Authority control instead, and improving that essay. Sławomir Biały (talk) 13:02, 17 May 2015 (UTC)
Floyd–Warshall algorithm
I could use some more eyes at Floyd–Warshall algorithm, please (see recent article history and talk page comments). —David Eppstein (talk) 23:08, 16 May 2015 (UTC)
Actuary FAR
I have nominated Actuary for a featured article review here. Please join the discussion on whether this article meets featured article criteria. Articles are typically reviewed for two weeks. If substantial concerns are not addressed during the review period, the article will be moved to the Featured Article Removal Candidates list for a further period, where editors may declare "Keep" or "Delist" the article's featured status. The instructions for the review process are here. SandyGeorgia (Talk) 02:09, 17 May 2015 (UTC)