Talk:Matrix (mathematics)

Coefficient of Linearity

When I search this term,- Coefficient of Linearity as a general search in Google, Lucky link is Coefficient of determination, I mean the first one what I am getting to.

But is that suffices, I have eye sight problem, unfortunately, Yes I read determination as differentiation at first sight. So got to writ over here again. I hope you folks can feel the difference. Maybe there is one, say Nabla or so.

First when I look at the article, it needs to be written even more as because the term Modern Algebra not referred. Means it can be driven with however the way you calculate so, addition, subtraction and so on of Matrices. Considering the one or more stands as Principal. Because it was not clearly explained by anyone so, rather been talked like what your book say so about it in this Talk page,- Talk:Matrix (mathematics) earlier & concluded and been edited, accepted.

Polynomial expansion clearly can be segregated for sure to more than one Linear Equation at its granularity, unless it reportedly dual by nature which might occur probably in Binomial Expansion very commonly. In any given non-linear equation, there exists at-least one Linearity. For anymore complexity, maybe by Principal,- Principal Matrix. So Editorial Team may intervene.

I disagree with Matrix addition, subtraction even if it is just Mathematics.

All I need is reference of Modern Algebra. It can be written well to have this compliance for fulfillment maybe to have clarity on Mathematical Proofing,- right, like, this has to be exactly should be done like this or could be done like this. The clarity that this Article needs.

—Dev Anand Sadasivam^t@lk 18:48, 11 August 2018 (UTC)

History

The section on 'History' mentions a very early use of matrices in China, then says that Cardano 'brought the method to Europe' in the 16th century. This might be interpreted as meaning that Cardano was aware of the ancient Chinese example and then introduced it to Europe. This seems highly unlikely. If it is not the intended meaning, I suggest the text should say just that Cardano was the first mathematician to use the method in Europe. Incidentally, the article on Cardano does not seem to mention his contribution to the subect.109.150.6.195 (talk) 20:33, 29 December 2019 (UTC)

Done. Seattle Jörg (talk) 07:40, 27 July 2021 (UTC)

See also section

I have edited the "See also" section for displaying the short descriptions of the linked articles. I leave to others to decide which links are relevant here. D.Lazard (talk) 11:29, 3 May 2020 (UTC)

Rectangular matrices with exact Inverse

Years ago, I seem to recall a Wikipedia page that showed examples of rectangular matrices that did not require SVD. I think some carried names. I've searched Wikipedia and Google, and now I find nothing. Any ideas on where to find such examples? Charles Juvon (talk) 21:25, 3 September 2020 (UTC)

Inconsistency -- what is a matrix?

The definition is unclear: in the very first sentence it is just a way of representation -- mathematical quantities in a rectangular array. In this sense, a calendar sheet that shows the dates of a month arranged by weeks would also be a matrix. Later comes the statement that you can add or even multiply matrices, which goes beyond that. Then, it again says that "major application of matrices is to represent linear transformations" (should probably read linear map), so if this is just the major application, calendar sheets would indeed fall into the category matrix. But then below under the heading "Definition" addition and multiplication are again required, and essentially all the rest of the article is about computations on matrices. Historically, Sylvester's introduction of the term also is only in the context of computability. I would argue to restrict the meaning of matrix here to those rectangular arrays of quantities that at least allow meaningful matrix multiplication, and I think that I am in line with most textbooks on that. Specifically, the introduction should reflect that explicitly. What are your thoughts on that? Seattle Jörg (talk) 07:39, 27 July 2021 (UTC)

Things are not as simple as it could appear: with your suggestion, an incidence matrix would not be a matrix. So, I suggest to expand the first sentence as follows, and to upgrade the article accordingly:

In mathematics, a matrix (plural matrices) is a rectangular array or table of numbers, symbols, or expressions, arranged in rows and columns, that is used to represent a mathematical object or a property of such an object. Generally, the operations on the represented objects are reflected by corresponding matrix operations. Without further specifications, matrices represent linear maps; their scalar multiplication, addition and multiplication correspond to scalar multiplication, addition and composition of linear maps.

By the way, the current lead is much too long, and contains to much technical details that belong to the body. IMO, the lead must be reduced to: the preceding quotation (or a variant of it); a short paragraph linking to other kinds of matrices and stating that the remainder of the article is about the matrices of linear algebra; a paragraph on square matrices; a paragraph on computational linear algebra and applications outside mathematics (this may be in the same paragraph, as most applications outside mathematics use computers). D.Lazard (talk) 09:16, 27 July 2021 (UTC)

I have rewitten the lead for fixing this issue. I have also removed many technical details that do not belong to the lead, for getting a lead of a reasonable length. The article body still requires to be updated, in particular for inserting in it details that I have removed from the lead, which were not duplicated in the body. D.Lazard (talk) 10:15, 28 July 2021 (UTC)

That's definitely an improvement, thank you. Seattle Jörg (talk) 11:10, 28 July 2021 (UTC)

No, it is not right. There are multiple problems. First, "without further specification" as no meaning. Can we say "here is a matrix of numbers but you are forbidden to multiply it by a vector"? Actually, mathematics is full of examples where matrices arise from a non-linear-algebra context but are then analyzed using linear algebra. Two examples are provided but claimed to be examples of the opposite: in combinatorics, adjacency and incidence matrices are defined as properties of discrete structures but there is a large industry of doing linear algebra with those matrices to analyze those structures. See spectral graph theory for one. An example of a combinatorial matrix which is rarely (but not never) regarded as a linear map is a Latin square. What the article can honestly report is that the most common use of a matrix in mathematics is to represent a linear map, and then immediately give an example (say $2\times 2$) to show what that means. Currently this use of a matrix is not even defined until much later in the article. Another thing: when a textbook like Lang defines "matrix" they are telling you what meaning the term has in the book. It doesn't mean that Lang would deny that, say, a Latin square is a matrix but only that it is out of scope in the context. It is different for an encyclopedia. McKay (talk) 04:37, 29 July 2021 (UTC)

The formulation "without further specification" can certainly be improved. The intended meaning if that, when one encounters the word "matrix" without any specification of the kind of matrix that is considered, this is in relation with linear algebra. This does not deny that other rectanguar arrays are called matrices (examples are given in the same paragraph). This does not deny either that these other matrices may have hidden relations with linear algebra (examples given in a footnote). IMO, the fact that, by default, a matrix represents a linear map, is important enough for appearing soon and clearly in the lead. By the way, your example of Latin squares is not really convenient here, as Latin squares are rarely called matrices, at least in Wikipedia article. D.Lazard (talk) 09:49, 29 July 2021 (UTC)

Latin squares are one of my specialties and I'd be very surprised if any of my colleagues denies that they are a type of matrix. But I'm not proposing they be mentioned in the lead. The major problem is that the lead says "Without further specifications, matrices represent linear maps" but not a clue is provided as to what that means. The poor reader has to find their way down to the "linear transformation" section and try to decode the explanation given there. McKay (talk) 08:00, 5 August 2021 (UTC)

I agree, this should be changed. And the lead contains details that should be left to the main text. --Andres (talk) 22:11, 8 October 2023 (UTC)

I've tweaked the wording to avoid the (unclear, at least to me) phrase "without further specification". --JBL (talk) 23:29, 8 October 2023 (UTC)

Format - matrix example

Thanks everyone for your input to create this. I believe the matrix example near the top should show the subscripts for the first two columns to be: a11, a21, a31, am1 and a12, a22, a32, am3 (the row subscripts are not indexing on the example). The last column follows the proper format. CarmenRx (talk) 13:08, 10 September 2023 (UTC)

This is possibly a problem of your viewer. On my laptop and my i-phone, the column indices are displayed correctly (in red). D.Lazard (talk) 15:34, 10 September 2023 (UTC)

Good call D.Lazard. It is the correct on my laptop (but not on my iPhone). CarmenRx (talk) 18:03, 10 September 2023 (UTC)

Numbers

In the first sentence, we read: ... table of numbers, symbols, or expressions, arranged in rows and columns, which is used to represent a mathematical object .... But numbers are mathematical objects. Some other wording is needed. English isn't my first language, so I cannot propose any better wording. --Andres (talk) 19:54, 8 October 2023 (UTC)

Symbols and expressions are also mathematical objects. I would suggest table of numbers, or other mathematical objects, arranged in rows and columns, which is used to represent a mathematical object that is associated to all entries of the table, but I am not sure that it is easier to understand. D.Lazard (talk) 20:05, 8 October 2023 (UTC)

The point is that objects and their signs (that are mathematical objects only qua types, not qua tokens) have to be distinguished. The objects themselves don't form any rectangle, their sign tokens do. Anyway, "rectangular array" isn't clear enough. Matrices aren't literally data types. --Andres (talk) 22:05, 8 October 2023 (UTC)

Essentially every reliable source on matrices uses the phrase "rectangular array" or equivalent, there is no possibility of it not appearing early and prominently in any discussion of what a matrix is. --JBL (talk) 23:36, 8 October 2023 (UTC)

Then this needs more explication. "Array" is linked to Array (data type). I don't think we should define matrices via data types. --Andres (talk) 23:43, 8 October 2023 (UTC)

I agree: "array" is used here in its simple common language meaning. I have removed the wikilink. --JBL (talk) 00:22, 9 October 2023 (UTC)

which is used to represent a mathematical object or a property of such an object

Matrices are mathematical objects on their own right. --Andres (talk) 10:05, 9 October 2023 (UTC)

Infinite matrices and empty matrices

It seems to me that neither infinite matrices nor empty matrices can be subsumed under the official definition, so the presentation is inconsistent. By the way, there is another generalization: hypermatrix. --Andres (talk) 22:16, 8 October 2023 (UTC)

It is true that infinite matrices are not matrices under the usual definitions, and also true that for many purposes it is sensible to class them with and study them alongside matrices. Roughly the same applies to matrices with 0 rows or 0 columns or both (though in some contexts they may in fact be admitted as matrices). Natural language is not a rigorous system, even in the context of natural language in mathematics.

Hypermatrices are mentioned briefly in the article, but under the alternative name "tensors". --JBL (talk) 23:34, 8 October 2023 (UTC)

This seems trivial to experienced mathematicians but I'm pretty sure that for beginners, lack of rigour can become an obstacle of understanding. Andres (talk) 23:46, 8 October 2023 (UTC)

It is not possible to develop, in an encyclopedic context, a rigorous treatment of the word "matrix" that is consistent across all uses, because those uses are not consistent with each other; this is not a flaw in the way the Wikipedia article is written, it is just the way life is. "Infinite matrix" is a very clear example of this, but so are thousands of other things; a common example is that "surfaces with boundary" are not surfaces under the usual definition. (Allowing myself to follow you in an off-topic direction: in my experience as an educator, beginners need to develop intuition before they can develop rigor, not the other way around.) --JBL (talk) 00:29, 9 October 2023 (UTC)

I agree that intuition should be developed before rigour. But once rigor begins, it should be really rigorous. Only when rigour is acquired, loose expressions become acceptable. So, then the article needs an intuitive introduction before the definition. I admit this would be the hardest part of writing the article. Andres (talk) 00:43, 9 October 2023 (UTC)

And oriented graphs are not graphs. I think this is no problem if this is clearly stated. --Andres (talk) 00:48, 9 October 2023 (UTC)

Of course they belong to the topic but I think it should be clearly and precisely stated how they relate to usual matrices. Andres (talk) 23:50, 8 October 2023 (UTC)

You are of course welcome to edit the article, or to make concrete proposals for changes. --JBL (talk) 00:30, 9 October 2023 (UTC)

Yes, maybe I will. --Andres (talk) 00:48, 9 October 2023 (UTC)

Subtraction

Under "basic operations" subtraction isn't mentioned (it is twice under generalizations). Matrix subtraction is a redirect to Matrix addition. But there subtraction isn't mentioned. Subtraction doesn't reduce to addition when we have no operation of opposite (opposite element, that is, inverse element as to addition). So we should have either subtraction or opposite among basic operations. --Andres (talk) 00:56, 9 October 2023 (UTC)

In the case of real and complex numbers the opposite is multiplication by –1. I don't know ho far this can be generalized. In any case, this should be mentioned, I think. --Andres (talk) 01:01, 9 October 2023 (UTC)

I have added subtraction, with other cosmetic changes. D.Lazard (talk) 11:40, 9 October 2023 (UTC)

"Matrix Theory and Linear Algebra" listed at Redirects for discussion

The redirect Matrix Theory and Linear Algebra has been listed at redirects for discussion to determine whether its use and function meets the redirect guidelines. Readers of this page are welcome to comment on this redirect at Wikipedia:Redirects for discussion/Log/2023 November 15 § Matrix Theory and Linear Algebra until a consensus is reached. Steel1943 (talk) 20:58, 15 November 2023 (UTC)

"Matrix(mathematics)" listed at Redirects for discussion

The redirect Matrix(mathematics) has been listed at redirects for discussion to determine whether its use and function meets the redirect guidelines. Readers of this page are welcome to comment on this redirect at Wikipedia:Redirects for discussion/Log/2023 November 15 § Matrix(mathematics) until a consensus is reached. Steel1943 (talk) 21:00, 15 November 2023 (UTC)