User talk:Jitse Niesen

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Away I am travelling 14 – 29 May and thus unable to respond promptly to queries, if at all. If there are issues with Jitse's bot, your best bet is to email me.

Unless requested otherwise, I will reply on this page, under your post. Sometimes, especially when we haven't met before, I copy my answer to your talk page. -- Jitse Niesen

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[edit] Parallelepiped volume.svg

Dear Jitse, your image "Parallelepiped volume.svg" is very nice, and would be very useful in parallelepiped. However, it is still misleading, notwithstanding the recent corrections (please see Talk:parallelepiped. Can you please fix it?

I also copied the image in triple product. Paolo.dL (talk) 14:49, 16 January 2008 (UTC)

I replied at Talk:parallelepiped. -- Jitse Niesen (talk) 16:48, 16 January 2008 (UTC)

[edit] {editprotected} at Template:Citation

Sorry to bother you, but could please you care of this {{editprotected}}? Thanks. -- Fullstop (talk) 02:10, 20 January 2008 (UTC)

I'm glad to help, but I was beaten to it. -- Jitse Niesen (talk) 12:38, 21 January 2008 (UTC)

[edit] Random maths article

May I ask where your random article tool gets its list of maths articles? It has just given me Sterling Fractal (deleted last June). Is this because it remains on List of fractal topics? Thanks. Algebraist 14:06, 22 January 2008 (UTC)

It gets it from List of mathematics articles (A) and List of mathematicians (A), and corresponding lists from the other letters, so it shouldn't give Sterling Fractal. I just had a look and discovered to my surprise that the data isn't updated daily. In fact, it hasn't been updated since June 2006! So, many thanks for your message. It should start using the new list from tomorrow. -- Jitse Niesen (talk) 14:18, 22 January 2008 (UTC)

[edit] Your bot

Your bot seemed to be sleeping last night and missed its archiving job at AFC. I'm going to have a go at doing it manually, but perhaps you could look into it for tonight? Thanks! MSGJ (talk) 13:39, 26 January 2008 (UTC)

Thanks for your message. It has been fixed. -- Jitse Niesen (talk) 18:34, 30 January 2008 (UTC)

[edit] Help with Matlab

Hey there...I'm very new here on wikipedia but I have seen that you are one of the most active editors on the Matlab article. I'm now building a program using one of the Matlab free open source extensions (psychtoolbox) and one thing that I should have in it is a good random number generator, something that Matlab failed to supply - I know about the Mersenne Twister for which there is a Matlab version but I can't find the open source-can you please help me with it?--Rogelp (talk) 16:58, 30 January 2008 (UTC)

I've never needed a better random number generator, so I'm not sure I can help you. I sometimes look on Matlab Central when I'm looking for code written by others. In this case, a search for "Mersenne twister" turns up a code by Peter Perkins. Is that suitable? I didn't try it. -- Jitse Niesen (talk) 18:34, 30 January 2008 (UTC)

Well, I find the needed solution (using unifrand and the computer clock...) so now, like you, I don't need a better RNG.

Best--Rogelp (talk) 13:48, 3 February 2008 (UTC)

Thanks

Thanks so much for encouraging me on my talk page. It was a positive in what can be a harsh academic world. You might visit the page for numeracy and have a look at the mathematical anxiety page I also started. I am now working in maths so anything positive has to be counted as helping me find gainful employment in my field. Feel free to reply to my talk page again. --Pete (talk) 10:15, 3 February 2008 (UTC)

[edit] Proposed deletion: etael equation

Yeah, I can't find my source either. Go ahead and delete it, I think I might have confused it with something else. —Preceding unsigned comment added by Kr5t (talk • contribs) 03:59, 4 February 2008 (UTC)

[edit] Images of Go

No problem, and my (real) name is Michelet, so everything is OK. Michelet-密是力-Me laisser un message 18:15, 8 February 2008 (UTC)

Make it "Linus Michelet" then, which will be specific enough. Everybody is entitled to a pseudonym... Michelet-密是力-Me laisser un message 18:22, 8 February 2008 (UTC)

[edit] Gauss-Newton algorithm

I started a discussion at Talk:Gauss-Newton algorithm in response to the rewrite of this article. Since you contributed a good part of the original article and are very familiar with the topic, I wonder if you could comment there. Thanks. Oleg Alexandrov (talk) 03:49, 9 February 2008 (UTC)

Commented there. -- Jitse Niesen (talk) 11:10, 12 February 2008 (UTC)

[edit] Random maths article again

Sorry to bug you about this, but this time it gave me symmetric prime (deleted January '07). Algebraist 11:10, 9 February 2008 (UTC)

Thanks. It seems like I updated the wrong file, sorry. It should work now. Don't hesitate to contact me again if you come across a deleted page. -- Jitse Niesen (talk) 11:10, 12 February 2008 (UTC)

[edit] Bot

User:Jitse's bot appears to be non-functional. The Evil Spartan (talk) 09:28, 10 February 2008 (UTC)

Thanks for your message. It's working again, and I set up a back-up on a different computer. -- Jitse Niesen (talk) 11:10, 12 February 2008 (UTC)

[edit] Question at Brent's method

I don't suppose you could address the problem discussed at Talk:Brent's method#D_declaration.3F relating to the lack of initialization for d in the supplied algorithm? I would assume that it should be 0 but it needs to be added if thats the case —Preceding unsigned comment added by 58.6.101.164 (talk) 13:46, 14 February 2008 (UTC)

Replied there. -- Jitse Niesen (talk) 13:55, 14 February 2008 (UTC)

[edit] Speedy deletion of Image:Airy plot.png

A tag has been placed on Image:Airy plot.png requesting that it be speedily deleted from Wikipedia. This has been done under section I1 of the criteria for speedy deletion, because the image is redundant copy (all pixels the same or scaled down) of an image in the same file format, which is on Wikipedia (not on Commons), and all inward links have been updated.

If you think that this notice was placed here in error, you may contest the deletion by adding {{hangon}} to the top of the page (just below the existing speedy deletion or "db" tag), coupled with adding a note on the talk page explaining your position, but be aware that once tagged for speedy deletion, if the article meets the criterion it may be deleted without delay. Please do not remove the speedy deletion tag yourself, but don't hesitate to add information to the article that would would render it more in conformance with Wikipedia's policies and guidelines. Hennessey, Patrick (talk) 02:24, 23 February 2008 (UTC)

[edit] Singular value decomposition

Thanks a lot for encouraging me at my talk page. Indeed that was me who was wrong. The SVD is unique up to multiplication of corresponding singular vectors by the same factor. I simply forgot about conjunction of the right singular vector which changes phase to -i\phi of it, and then matrix multiplication yields the same result... (You may think about it as a rotation of corresponding singular spaces by the same angle in complex plane) I undid my edit. Sorry for the confusion

Merilius (talk) 20:00, 4 March 2008 (UTC)

[edit] Taylor Series error approximation

Yes, the taylor polynomial page has an explanation on the error term, but for any high school student trying to learn about how to approximate the error of a taylor series polynomial won't know what it means. Math should be expressed simply, accessible to someone who wants to learn about it. —Preceding unsigned comment added by Dspdude (talk • contribs) 01:03, 10 March 2008 (UTC)

Of course we should try to express maths simply, but I don't see what that has to do with it. If you think that you can improve the explanation of the error in Taylor polynomial, I suggest you change it there. -- Jitse Niesen (talk) 11:14, 10 March 2008 (UTC)

[edit] empty matrices

Dear Jitse Niesen

(I'll not write in Dutch, in case other people should read this). I saw you recently removed a part of my text on empty matrices. That's OK with me, it was probably a bit pedantic. And I like the reference although I cannot access the linked to article. But I do not entirely agree with your edit summary that the current mathematical definition already deals with this point. The definition suffices to represent and distinguish all n×k for given n and k, even if they have no coefficients, as these are represented by the (empty) map from the empty set of the set of possible coefficients. However, there is only one such map, so all empty matrices get represented by the same object, from which it is impossible to reconstruct n and k. This even holds if maps are provided with information that tells what is their domain and range (as there is just one empty set). So if one wants to construct a universe in which matrices of all possible sizes live together, and where those matrices that allow it can be multiplied, then some extra information should be included in matrix values so that n and k can be unambigously reconstructed from any matrix. That was the point of my remark. Marc van Leeuwen (talk) 18:06, 11 March 2008 (UTC)

You're of course right. I did understand that that was the point of your remark. However, I thought that the formal definition in the article, which identifies matrices with functions

$\{1,2,\ldots,m\} \times \{1,2,\ldots,n\} \to \mathbb{F},$

includes this information (using the definition of a function as a 3-tuple domain, codomain, graph). I did not appreciate that the Cartesian product $\{1,2,\ldots,m\} \times \{1,2,\ldots,n\}$ is the same (viz., the empty set) if m = 0, whatever value n has. To my defense, Carl de Boor is not very clear on this point (I think you can download his article from http://ftp.cs.wisc.edu/Approx/empty.pdf ).

It is a bit pedantic, but to be honest, I think the whole section goes a bit too much into detail given the context. Perhaps it's best to move it to a new article, empty matrix, and leave just one sentence in matrix (mathematics) pointing to that article. What do you think of that?

Anyway, I'll put your remark back in and added another reference I stumbled upon. It's a pity that neither reference has a formal definition along the lines of your "pedantic computer science" definition. -- Jitse Niesen (talk) 11:45, 12 March 2008 (UTC)

Thanks for the article, which does not in fact discuss how to distinguish empty matrices, although it does mention their distinctiveness. As for the idea to create a separate page for empty matrices, that could be a good idea, although I fear that they fail to meet the wikipedia's notability criterion. Maybe some page discussing multiple "empty" issues could suit the purpose; there is already some of this stuff out there. I'll give it a thought. Marc van Leeuwen (talk) 20:41, 12 March 2008 (UTC)

[edit] User-script manager

Certain user's are expressing concerns with the User-Script Manager. User pages, subpages including monobook.js & monobook.css files are apparently appearing in the AFD Category, it happened to me once as you can view via [1] i stopped using the scripts from the Script Manager awhile back but apparently more user's are experiencing the same problem just thought you should be informed of the event and hope you could find what scripts or bugs are causing this to happen. Terra ^{What do you want?} 19:43, 13 March 2008 (UTC)

I think the whole idea of the user-script manager is no longer useful now that we have Wikipedia:Gadgets. I don't feel like going through the code and fixing it, so instead I removed the whole functionality. -- Jitse Niesen (talk) 19:38, 15 March 2008 (UTC)

[edit] Part (mathematics)

Sure, I don't mind. Basically the sequence was: a) I went to the Part page, and saw that it was a disambig page that looked nothing like one b) There was some information there relating to mathematics, which I figured probably belonged somewhere, but not on a disambig page c) I created somewhere for this content to live

It seems to me that whoever wrote the original content thought that there was a special meaning for "Part" in mathematics, but I could be wrong.

Anyway, to me, the best solution would be if someone who knew more than me about mathematics could find somewhere for that content to live, and then link it from the Part page. But I'm not attached to anything except that the disambig page should look like the other wikipedia disambig pages; feel free to just change stuff, and if I don't like it, I'll complain.

--TimNelson (talk) 02:12, 14 March 2008 (UTC)

[edit] Question about Jitse's bot

Could you take a look at WT:WikiProject_Articles_for_creation#Categories and see if I'm sane? Thanks! Yngvarr (c) 15:59, 14 March 2008 (UTC)

Replied there. -- Jitse Niesen (talk) 23:30, 19 March 2008 (UTC)

Thanks; Very much appreciated. Yes, I'm new to this.

--Tangi-tamma (talk) 22:27, 17 March 2008 (UTC)

[edit] RfC

I've started drafting a user conduct RfC that you might be interested in here. There's a lot of evidence to sift through and present, so I think it will take awhile to get it put together. If you'd like to participate, please feel free to do so. Cla68 (talk) 07:47, 28 March 2008 (UTC)

[edit] Hello

I've seen your important contributions for the article Recurrence relation. I'm looking for the general (non-iterative) algebraic expression for the exact trigonometric constants of the form: $\begin{align}\cos \frac{\pi}{2^n}\end{align}$ , when n is natural (and is not given in advance). Do you know of any such general (non-iterative) algebraic (non-trigonometric) expression?

Let me explain: if we choose n=1 then the term $\begin{align}\cos \frac{\pi}{2^n}\end{align}$ becomes "0", which is a simple (non-trigonometric) constant. If we choose n=2 then the term $\begin{align}\cos \frac{\pi}{2^n}\end{align}$ becomes $\begin{align}\frac{1}{\sqrt{2}}\end{align}$ , which is again an algebraic (non-trigonometric) constant. etc. etc. Generally, for every natural n, the term $\begin{align}\cos \frac{\pi}{2^n}\end{align}$ becomes an algebraic (non-trigonometric) constant. However, when n is not given in advance, then the very expression $\begin{align}\cos \frac{\pi}{2^n}\end{align}$ per se - is not an algebraic expression but rather is a trigonometric (non-algebraic) expression. I'm looking for the general (non-iterative) algebraic (non-trigonometric) expression equivalent to $\begin{align}\cos \frac{\pi}{2^n}\end{align}$ , when n is not given in advance. If not for the cosine - then for the sine or the tangent or the cotangent.

Eliko (talk) 08:26, 31 March 2008 (UTC)

No, I don't know any such expression. -- Jitse Niesen (talk) 11:18, 31 March 2008 (UTC)

Thank you. Eliko (talk) 11:22, 31 March 2008 (UTC)

To Eliko: I think that for which you are asking is impossible. You want a closed polynomial with radicals, f (n), which satisfies: f (1) = 0; and 2·(f (n+1))² = 1 + f (n) for all n. I do not think that there can be any such thing. What degree (maximum power of n) would the formula have? JRSpriggs (talk) 11:32, 31 March 2008 (UTC)

The formula is not supposed to have a degree. Does Fibonnaci formula have a degree? Eliko (talk) 11:38, 31 March 2008 (UTC)

Well, if you are going to allow exponential formulas (like the Fibonnaci formula) rather than merely algebraic formulas, then why not simply replace the cosine by its exponential expression? $\cos\theta = \frac{e^{i \theta} + e^{-i \theta}}{2}$ JRSpriggs (talk) 12:29, 31 March 2008 (UTC)

Your exponential expression is over the imaginary numbers, i.e. (according to Euler's formula) this is a trigonometric formula. I'm looking for a non-trigonometric formula (hence for a formula which is non-exponential-over-the-imaginaries). However, if it has not been sufficiently clear in my previous request - then you can add it now as an additional condition: non-trigonometric and non-exponential-over-the-imaginaries. Eliko (talk) 12:43, 31 March 2008 (UTC)

I hope you realize that it is easier to calculate trigonometric functions than real exponential functions. Instead of imposing a series of rather arbitrary and unclear conditions, why do you not explain for what you want to use this? JRSpriggs (talk) 02:46, 1 April 2008 (UTC)

This is an abstract question in pure mathematics. However, any solution may be helpful in answering other questions, like: finding a non-trigonometric proof for the following non-trigonometric claim: Every real interval includes a point x having a natural number n such that $\begin{align}(x+i)^n\end{align}$ is a real number. Note that this is an algebraic, non-trigonometric claim, so one may naturally expect that it may be proven by a non-trigonometric proof. Eliko (talk) 14:33, 1 April 2008 (UTC)

I think that your conjecture is probably true. However, to think that you can excise trigonometry from mathematics and expect what remains to hang together and function normally is unreasonable. JRSpriggs (talk) 07:53, 2 April 2008 (UTC)

What you call my "conjecture" - is actually a sentence (proven by trignometric means). However, there are many sentences which can be proven by both trigonometric means and non-trigonometric means (e.g, the sentence claiming that $\begin{align}(-1)^n\end{align}$ is either 1 or -1 for any natural n, etc.), so one may naturally expect that also the other (first) sentence may be proven by a non-trigonometric proof. So the abstract question (in pure mathematics) is now: whether any such non-trigonometric proof does exist (just as it exists in other fields). Eliko (talk) 11:20, 2 April 2008 (UTC)

I suspect that you mean "theorem" rather than "sentence". I would think that the way to prove it would be to expand the power using the binomial theorem and then take the imaginary part and set it to zero. Then use the theorems about the number of roots of a polynomial as a function of the sign changes of its coefficients. JRSpriggs (talk) 05:15, 4 April 2008 (UTC)

You're definitely correct: I really meant "Theorem".

Unfortunately, I've never heard of "theorems about the number of roots of a polynomial as a function of the sign changes of its coefficients". Would you care to elaborate on those theorems (of which I've never heard), or to let me read about them on Wikipedia? Thank you in advance.

Anyways, "my" theorem states that the root belongs to a given interval, so I really don't know how "your" theorem (about the number of roots, rather than about the interval to which a root belongs) can help here. Eliko (talk) 08:08, 4 April 2008 (UTC)

(Unindenting) Unfortunately, I do not remember the name of the theorem or all the details, but there is a relationship between the number of sign changes in the coefficients and the number of positive roots. Since you can shift a root past zero by a simple substitution x = y+c for an appropriately chosen constant c, this gives a way to show that there must be a root in an interval (see also Viète's formulas). Or you could just increase n until you have both a positive and a negative value of the polynomial in the desired interval. Then there must be a root between them by the intermediate value theorem. JRSpriggs (talk) 11:11, 6 April 2008 (UTC)

As to your first proposal: Let's assume that our interval is (a,b). Now, for every constant c we can really substitute: x = y+c, and then x can belong to the interval (a,b) if and only if y can belong to the interval: (a-c, b-c). However, I really don't know how you can prove (without any trigonometric means) that y can really belong to the interval: (a-c, b-c).
By the way, Viète's formulas (for the sum of roots or for the product of roots etc.) - is well known, but it does not promise that (at least) one of the roots is real (as I want it to be), unless n is odd, but even when n is odd - some of the roots may still be unreal, so I really don't know how Viète's formulas are relevant for proving the existence of a (real) root which belongs to a given (real) interval.
As to your second proposal: I really don't know how you can prove (without any trigonometric means) that there really exists such an n "having both a positive and a negative value of the polynomial in the desired interval".

Eliko (talk) 12:29, 6 April 2008 (UTC)

JRSpriggs, you may be thinking of the Descartes' rule of signs or Sturm's theorem. -- Jitse Niesen (talk) 13:29, 6 April 2008 (UTC)

Cheers, Thank you; But I still don't know how these theorems may be helpful for proving the existence of roots within a given interval, as I've explained above. Eliko (talk) 13:37, 6 April 2008 (UTC)

To Jitse: Yes, thank you. I was thinking of Descartes' rule of signs, but Sturm's theorem (which I had not seen before) looks even better for this purpose. JRSpriggs (talk) 13:42, 6 April 2008 (UTC)

More precisely: Descartes' rule of signs is totally irrelevant here, because when we expand the power of $\begin{align}(x+i)^n\end{align}$ and set the imaginary part (of the received polynomial) to zero, then every two consecutive coefficients in the second polynomial include a zero, whereas Descartes' rule of signs is about consecutive nonzero coefficients. On the other hand, Sturm's theorem could have been relevant, but unfortunately it's about a (natural) n given in advance, so Sturm's theorem does not promise the very existence of such a (natural) n. My theorem states that such a (natural) n really exists. Eliko (talk) 14:03, 6 April 2008 (UTC)

I believe that Descartes' rule of signs does not require that all coefficients be non-zero. It works for sign changes between coefficients which are consecutive among the non-zero coefficients. For example, it implies that x² - 1 = 0 has one positive real root because there is one sign change. Similarly, x⁵ - x + 1 = 0 must have either two or zero positive real roots. That is, skip over zero coefficients as if they were not there. JRSpriggs (talk) 07:07, 8 April 2008 (UTC)

If your conjecture is true, i.e. Descartes' rule of signs really allows zero coefficients to be skipped over as if they were not there, then Descartes' rule of signs could really have been relevant, but unfortunately it's about a (natural) n given in advance, so Descartes' rule of signs does not promise the very existence of such a (natural) n. My theorem states that such a (natural) n really exists. Eliko (talk) 09:17, 8 April 2008 (UTC)

[edit] Trouble with MathML

I'm sorry for coming out of the blue, but your name is referenced on the the relevant Mediawiki page as the person who is still working on this. I've just accepted the way the wiki generates formulae for quite some time now, but I've had it. I want my own system's better looking fonts to render them. I'm using FF 3.0 and I have both Matlab *and* Maple installed, so I know I have the high quality fonts installed in the system directory that are needed to support MathML. I've long since switched "on" the preference in my Wikipedia CP to enable MathML. Still, all I get are crummy rendered images. It is really annoying and the WP Formula authoring page is not helpful. What, oh what, must I do to get my MathML? Thanks in advance. --Dragon695 (talk) 23:44, 3 April 2008 (UTC)

The MediaWiki software that is running the website cannot do MathML. There is indeed an option in the preferences, but it doesn't do very much; only some extremely simple formulas are done in MathML, the rest uses rendered images as normal.

I did work on better support for MathML for a while, but I stopped this project. It's not as easy as I thought, support for MathML in the browsers is quite patchy, and I got almost no feedback from the programmers behind MediaWiki. So, I'm afraid it's not possible to get MathML on Wikipedia. -- Jitse Niesen (talk) 14:01, 6 April 2008 (UTC)

[edit] QR_Decomposition

Hi, thank you for your revision on article of QR_Decomposition. I am not sure which definition is ``more standard. As far as I know, both of these two definitions exist. The first one (A is mxn, then Q is mxm, R is mxn) is used in many textbooks and also many numerical applications, such as LAPACK and Matlab. But the second one does exist too. Since I believe the first one may be used more frequently (partly due to the popularity of Matlab etc), I select it as the first candidate and the original one as an alternative one. It is just my personal opinion. Please correct me if necessary. —Preceding unsigned comment added by Realwhz (talk • contribs) 17:39, 7 April 2008 (UTC)

[edit] Question on Brent's method

Hi, could you maybe take a look at the question I asked on Brent's method's talk page? Thanks! laug (talk) 13:22, 10 May 2008 (UTC)

[edit] Advanced examples of mathematical induction

Hello there, I wonder if you would take the time to read the deletion discussion for Proofs involving the totient function (deletion discussion) The article on mathematical induction has the same format and cites an authoritative source, namely Mathworld. I don't understand why you would vote to keep one but not the other. The article on induction could be the start of a useful series of advanced examples, same as the totient function article. -Zahlentheorie (talk) 13:59, 10 May 2008 (UTC)

I didn't comment at the deletion discussion for Proofs involving the totient function, but if I had been forced to comment, I would have said that it doesn't belong on Wikipedia. The people that did comment were obviously of another opinion. I think the difference between Proofs involving the totient function and your article is that the former article is meant as a further elaboration of totient function in that it provides proofs of statements listed there, while your articles gives examples of proofs and is thus too much textbook material and not really encyclopaedia material. Another, less satisfactory, explanation is that we are not consistent in our deletion discussions; it is unfortunate but the outcome of a deletion discussion depends on which people participate in it.

Adding proofs to Wikipedia is a hazardous activity. Some people, including myself, think that detailed proofs do not belong here (with some exceptions, like Cantor's diagonal argument). Others disagree. If you do add a proof, especially an article solely about a proof, there is a decent chance it is deleted. I'm sorry you found this out only after all the work you put into it. -- Jitse Niesen (talk) 13:41, 12 May 2008 (UTC)

[edit] Winograd algorithm

Hi! Sorry, I managed not to see your comment on this talk page, so it took me almost a year to respond. Better late than never though, I guess :) -- Obradović Goran (ta^lk 20:10, 17 May 2008 (UTC)

[edit] New articles not showing up?

Hi, I noticed that new articles aren't showing up at the Wikipedia:WikiProject_Mathematics/Current_activity. I don't know if it just takes them a little longer to make themselves known to User:Jitse's bot or if the bot is having problems. Anyway, I thought I should bring it to your attention. siℓℓy rabbit (talk) 12:57, 4 June 2008 (UTC)

This actually goes back to mathbot, the machine on which it runs is down, and then nothing feeds Jitse's bot. I notified the system people about the machine, hopefully it will get fixed soon and all will come back to normal. Oleg Alexandrov (talk) 15:24, 4 June 2008 (UTC)