User talk:David Eppstein

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Hi, and welcome to my User Talk page! For new discussions, I prefer you add your comments at the very bottom and use a section heading (e.g., by using the "New section" tab at the top of this page). I will respond on this page unless specifically requested otherwise. For discussions concerning specific Wikipedia articles, please include a link to the article, and also a link to any specific edits you wish to discuss. (You can find links for edits by using the "compare selected revisions" button on the history tab for any article.)

William B. Cassel

Okay, I'll omit it altogether then (the DOB) but there are THOUSANDS of articles where the birthdate is not sourced so I don't see what difference it makes. I get the point of the guidelines and understand them, but why only apply them to certain articles and not all of them uniformly? Thanks. Snickers2686 (talk) 06:51, 1 January 2018 (UTC)

If you find other biographies of living people with unsourced birth dates or other such information, please do something about them. The same standards should apply to all. —David Eppstein (talk) 06:54, 1 January 2018 (UTC)

January 2018

You currently appear to be engaged in an edit war according to the reverts you have made on 209 (number). Users are expected to collaborate with others, to avoid editing disruptively, and to try to reach a consensus rather than repeatedly undoing other users' edits once it is known that there is a disagreement.

Please be particularly aware that Wikipedia's policy on edit warring states:

  1. Edit warring is disruptive regardless of how many reverts you have made.
  2. Do not edit war even if you believe you are right.

If you find yourself in an editing dispute, use the article's talk page to discuss controversial changes; work towards a version that represents consensus among editors. You can post a request for help at an appropriate noticeboard or seek dispute resolution. In some cases it may be appropriate to request temporary page protection. If you engage in an edit war, you may be blocked from editing.
I warned the person adding the material; I probably should warn you that you have technically reverted 3 times today, as well...Arthur Rubin (talk) 03:07, 2 January 2018 (UTC)

Yes, that's where I stopped. But by my count Genesyz is now up to six, three of them after I stopped... —David Eppstein (talk) 04:39, 2 January 2018 (UTC)
Template the regulars! EEng 04:42, 2 January 2018 (UTC)
...and now you've used your three reverts, and Genesyz is up to eight. Someone else want to take up the baton, or will the edit warring noticeboard notice first? —David Eppstein (talk) 05:14, 2 January 2018 (UTC)
[1] EEng 05:18, 2 January 2018 (UTC)
And now we have proof that it's insignificant: he's referencing it to Smarandache. —David Eppstein (talk) 05:27, 2 January 2018 (UTC)

Number categories

Because Category:Surfaces was categorized under Category:2 (number) (being two dimensional), I added Line (geometry) under Category:1 (number) and Volume under Category:3 (number) as 1 and 3 dimensional respectively. If you uncategorize Line, please also uncategorize Surfaces. Dpleibovitz (talk) 19:09, 4 January 2018 (UTC)

  • I categorized length under 1, area under 2 and volume under 3. Dpleibovitz (talk)

Indent in 209

that was me. We have

  • Properties of 209
  • Another property of 209
    discussion [line in question]
  • Another property of 209
  • ...

WP:ACCESS suggests it should be "*:" or "*", and I think "*:" better indicates the connections. — Arthur Rubin (talk) 21:19, 5 January 2018 (UTC) ────────────────────────────────────────────────────────────────────────────────────────────────────

If it were not part of a bulleted list, it would be

start of paragraph about a property


rest of paragraph about a property

Because it is in a bulleted list, this should all be indented one level, under a single bullet:

  • start of paragraph about a property
rest of paragraph about a property

It is incorrect to indent the rest of the paragraph at the formula level, and it is also incorrect to start a new bullet. —David Eppstein (talk) 21:32, 5 January 2018 (UTC)


I just took a look at your photos. Wow! You do good work. Keep it up. I do a bit myself, but my oldest brother is the real artist and photographer in our family. We always had a darkroom in our house. He's an artist with some famous people as customers: Reagan, Loni Anderson (nude), etc. He primarily does portraits and large murals. Due to age (77) he's slowing down. -- BullRangifer (talk) 06:57, 8 January 2018 (UTC)

Thanks! I'm pleased with how my latest batch came out but I feel like I haven't been doing enough of that lately. Too much Wikipedia editing instead... —David Eppstein (talk) 07:05, 8 January 2018 (UTC)
That's understandable. You're a busy man. Your work in education is very important. My parents were college teachers, and travel and education were always high priorities in our family. Although my first college major was computer programming, back when it was a new thing, what you do is "Greek to me". It's way over my head. Otherwise, keep up your work here. We need people like you. It can be daunting, exhausting, and discouraging. There are so many subjects, and I like to cover many. I recently pared my watchlist down from over 8,000 to about 400. Now it's already crept back up and is at 576. I need to watch that it doesn't get so high again. -- BullRangifer (talk) 07:19, 8 January 2018 (UTC)

Finding references for computer science or mathematics articles

Hi there, I wanted to thank you for all your help with Prime number. I'm still new to Wikipedia though and I was wondering if you had any advice for finding references for CS or math material. Due to the nature of the content it is quite difficult sometimes to find a particular bit of content on Google. For instance, I wanted to add to an article a bit about the advantage of insertion sort over selection sort when using non-sequential storage media, i.e. insertion sort requires a magnetic disk to travel less than selection sort. It is quite easy to prove and I'd have no problem adding the entire proof if needed, but alas, it would be a paragraph without an independent source as a reference Derek M (talk) 03:28, 17 January 2018 (UTC)

I tend to use Google Scholar and Google Books instead of the usual web searches for this sort of thing. Searching Google scholar with the quoted strings "insertion sort" "selection sort" finds some comparisons, but I'm not sure what the right keywords would be for the non-random-access media. —David Eppstein (talk) 03:52, 17 January 2018 (UTC)
If I truly can't find a reference, is it acceptable to cite myself in the meantime, or is it better to add {{Citation needed}}? I read this to see if I could get away with leaving no citation at all but I think that section is not really intended for mathematical proofs. Derek M (talk) 20:44, 17 January 2018 (UTC)
Self-citations can be ok, when you can't find anything better elsewhere, but it would need to be a reliably published source and not just a blog post or personal calculation. —David Eppstein (talk) 21:10, 17 January 2018 (UTC)

Women in Red editathon on mathematicians

Hi there, David! There has recently been renewed interest in mathematicians on WiR following this article by Mvitulli. As a result, we have decided to provide focus on mathematicians in February. You'll find the editathon page here. As you have been so active on women mathematicians, I though I should give you advance notice. We'll be sending out invitations soon but in the meantime, feel free to let your mathematician friends know about it. I hope you will find time to participate enthusiastically yourself.--Ipigott (talk) 15:18, 21 January 2018 (UTC)

Thanks for the heads-up. I posted about this editathon on my G+. —David Eppstein (talk) 07:02, 24 January 2018 (UTC)

great work!

Hi, great work with the Burkard Polster article! You rescued it and then you made it so much better. I wouldn't have known how to make 10% of the improvements that you made. DrVogel (talk) 14:15, 23 January 2018 (UTC)

You're welcome! I was just at Monash a month ago but never actually had a chance to meet Polster. —David Eppstein (talk) 16:37, 23 January 2018 (UTC)
haha what a missed opportunity! DrVogel (talk) 01:41, 24 January 2018 (UTC)

Fernando Codá Marques

Is the article Fernando Codá Marques at almost the level of a GA? (is this the name for those who have the green symbol at the top?) How to turn it into a Featured article? All the info is sourced and the article is in very good shape. Sorry for my English (I find it hard to write in this language)... There is a very high chance he will be a Fields Medalist this year (either he or Simon Brendle will win it is said "everywhere"). I think it would be nice if we had the article in even better shape before that happen, so that it can appear at the main page. What do you think? Best, —Viktor (talk) 11:57, 26 January 2018 (UTC)

I don't think so. The bulk of the article is one big section that does not distinguish between his career steps, mathematical accomplishments, and recognition for those accomplishments. The works and honours sections look like lists not prose. And far too many of the sources are primary rather than secondary. Compare with Andrew Gleason, an actual GA. —David Eppstein (talk) 15:35, 26 January 2018 (UTC)
Looking with more care, I do agree with you! (talk) 17:23, 26 January 2018 (UTC)
I am the IP, I think it's better to edit logged, but sometimes I am too lazy to log in, haha... I will try to improve the article taking the page you mentioned as example. Thanks! Flannán (talk) 17:39, 26 January 2018 (UTC)
There is an in-depth article about him in a Brazilian magazine:éis.revista.piauí_djvu.txt . I think it may be better to wait for more in-depth articles about him, which will appear, specially if the predictions get confirmed, and then it will be much easier to improve the Wiki article. Flannán (talk) 17:47, 26 January 2018 (UTC)
Maybe the article is now more of a mess than it was before, but I've followed Be bold!, haha. Best, Flannán (talk) 18:04, 26 January 2018 (UTC)

About the reverting of my edit on Hedetniemi's conjecture 's talk page

I see that you reverted my addition of the ratings template. I admit I don't know much about the importance of this article. But I believe it needs to have a ratings added. There are a lot, really a lot of math articles with missing ratings template, and by adding them we can help keep track of the progress of various math articles in the WikiProject Mathematics. So I strongly suggest you just change the ratings to B or C or whatever; just don't delete the ratings template. At least that's how I see it. I am currently working through a list of graph theory topics, adding such templates. I use low importance and stub/start levels by default according to how much references it has, plus the general length of the article, unless I recognize the importance right away, like Petersen graph for example. If you don't object to my reasoning, I would like to put the ratings template back there, though not right away. If you do object, explain why not, please! Thanks! --TheBlueWizard (talk) 03:33, 28 January 2018 (UTC)

@TheBlueWizard: If you're going to be mass-rating articles you should learn to distinguish between start class and C class. In particular, your idea that "stub/start" levels are a good default is wrong; "start" does not mean "recently started", it means "weak in many areas", "prose may be distinctly unencyclopedic, and MoS compliance non-existent", "frequently, the referencing is inadequate". If a new article is of reasonable length, well structured, and with significant sourcing it's probably B or C; choosing which of B or C it is usually requires that you understand the subject well enough to assess whether it's more or less complete or whether there are important topics still missing. Read and pay attention to the detailed guidelines at Wikipedia:WikiProject assessment. Also, rating everything "low" importance is also a bad default; importance rating requires, again, that you have significant knowledge of the general subject area, not just a superficial "have I heard of this before". So yes, I object. I think that bad ratings are less useful than no ratings, and will continue to remove them when I see them. —David Eppstein (talk) 03:59, 28 January 2018 (UTC)
OK, how about putting up a ratings template without any ratings at all (so that they would appear as class: ???, importance: ???). That way I can see how many math articles there are in the ratings statistics? Will that do? If you don't like that, then I don't see the point of organizing the math articles at all, and I will go do something else on Wikipedia. What do you say? P.S. I think WikiProject Mathematics could use some improvement, though I am not sure... --TheBlueWizard (talk) 05:40, 28 January 2018 (UTC)
If you add blank ratings templates I certainly won't revert you, although I'm not entirely sure what the point is. Why do you think it is more important to spend your time on this and yet to skip past blatant blatant problems on the articles you rate without correcting them (e.g. oversized image filling the entire screen on Dejter graph, now fixed)? —David Eppstein (talk) 05:43, 28 January 2018 (UTC)

Feburary 2018 at Women in Red

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Welcome to Women in Red's February 2018 worldwide online editathons.
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New: "Black women"

New: "Mathematicians and statisticians"

New: "Geofocus: Island women"

Continuing: #1day1woman Global Initiative

(To subscribe: Women in Red/English language mailing list and Women in Red/international list. Unsubscribe: Women in Red/Opt-out list) --Rosiestep (talk) 14:32, 28 January 2018 (UTC) via MassMessaging

Your GA nomination of Prime number

Hi there, I'm pleased to inform you that I've begun reviewing the article Prime number you nominated for GA-status according to the criteria. Time2wait.svg This process may take up to 7 days. Feel free to contact me with any questions or comments you might have during this period. Message delivered by Legobot, on behalf of Jakob.scholbach -- Jakob.scholbach (talk) 15:00, 28 January 2018 (UTC)

Wow, that was fast — thanks! Usually this sort of nomination languishes for months waiting for a reviewer. —David Eppstein (talk) 17:50, 28 January 2018 (UTC)

Both Tonelli-Shanks and Cipolla's modular square root algorithms can handle powers of prime modula (not just primes)

Hi David,

I looked up Dickson's History of Numbers vol 1 p215(Tonelli) and p218(Cipolla) and Dickson clearly shows that both modular square root algorithms can handle powers of prime modula (whereas the Wiki articles say they can only do prime modula).

I've updated the TALK pages of both articles with the relevant Dickson math, along with numeric runthroughs with Mathematica code.

However, I am not a professional mathematician so I hesitate to update the articles.

Perhaps yourself, or someone else in the Computer science field could update the relevant articles with this information from Dickson.

The articles in question are:

Tonelli–Shanks algorithm
Cipolla's algorithm

Endo999 (talk) 02:37, 30 January 2018 (UTC)

About my edits around "Prime number"

This is more about my feeling of your perception of my edits than about the quality of the article, therefore I came here. Since I got the impression that you were annoyed or at least bothered by my edits, I firstly want to apologize for my inadvertently destroying your ALT-caption. I should have been more attentive. Next I want to assure that I never wanted to cause any annoyance or bothering, I really only act in good faith, and only when I am reasonably sure about my reasons to edit. My introduction of "primorial" and its primes to the article was based on my impression that primorial itself were not included at all (outside of references), and the associated primes were only mentioned once (and linked) within an entry of a table. I regret not having had sources readily at my hands; and on this occasion I want to express my admiration of the work you have done to this article, not only regarding sourcing. Inserting my edit under "Other mathematical applications" was triggered by the paragraph about theorems by Sylow, Lagrange and Burnside re primes and finite groups, associating myself the construction of the primorial function with primes.

Finally, I hope my suggestions in the TP about the structure of the article reflect some rational thoughts, and are not considered as disturbing the expectably successful GA-review process. Congrats in advance. Purgy (talk) 07:55, 30 January 2018 (UTC) the alt-caption, not particularly annoyed; I only found out about MOS:ALT very recently so my expectation is that nobody else knows about it either. I was a bit annoyed by your adding a paragraph without any sources on primorial, though, after I spent considerable effort as part of GA prep to make sure every claim in every sentence was properly sourced. Other than that although I disagreed with some of your edits I don't think I considered any of them ill-considered. —David Eppstein (talk) 08:38, 30 January 2018 (UTC)
... to be honest, and hopefully not too much increasing your annoyance level about me: I strongly hoped for you having ready at hand some appropriate sources for my amendments. I repent ... ;) Purgy (talk) 10:12, 30 January 2018 (UTC)
Google book search for "primorial" finds mainly cranky sources associated with Smarandache, or sources talking about what we already mention, the search for primorial primes. I think that's because "primorial" is one of those notions that we cover here out of proportion to its importance, because (unlike more important aspects of the subject) it's easy to understand. But primorials are not actually especially important. Compare factorials, which are hugely important in combinatorics (counting permutations), functional analysis (the power series for the exponential function), etc., and somewhat important in number theory because they eventually include all divisors. Primorials have none of that. What good are they, besides being near somewhat large prime gaps (something we also mention, in a footnote)? I'm not suggesting that primorials are non-notable or shouldn't have an article, I just don't see them as a significant aspect of the theory of prime numbers, not like unique factorization or the prime number theorem or primality testing algorithms etc. —David Eppstein (talk) 16:33, 30 January 2018 (UTC)
Thank you, cordially, for your patience with my disputatious behaviour. For not to abuse your TP any longer, I'll take my next suggestion to the article's TP. Purgy (talk) 10:58, 31 January 2018 (UTC)

Your GA nomination of Mark Barr

Congratulations! Your GA review has begun!

Hi there, I'm pleased to inform you that I've begun reviewing the article Mark Barr you nominated for GA-status according to the criteria. Time2wait.svg This process may take up to 7 days. Feel free to contact me with any questions or comments you might have during this period. Message delivered by Legobot, on behalf of Wilhelmina Will -- Wilhelmina Will (talk) 05:00, 31 January 2018 (UTC)

February 2018

Commons-emblem-notice.svg This message contains important information about an administrative situation on Wikipedia. It does not imply any misconduct regarding your own contributions to date.

Please carefully read this information:

The Arbitration Committee has authorised discretionary sanctions to be used for pages regarding all edits about, and all pages related to post-1932 politics of the United States and closely related people, a topic which you have edited. The Committee's decision is here.

Discretionary sanctions is a system of conduct regulation designed to minimize disruption to controversial topics. This means uninvolved administrators can impose sanctions for edits relating to the topic that do not adhere to the purpose of Wikipedia, our standards of behavior, or relevant policies. Administrators may impose sanctions such as editing restrictions, bans, or blocks. This message is to notify you that sanctions are authorised for the topic you are editing. Before continuing to edit this topic, please familiarise yourself with the discretionary sanctions system. Don't hesitate to contact me or another editor if you have any questions.

Coffee // have a ☕️ // beans // 05:47, 2 February 2018 (UTC)

Continue to encourage that behavior and you will face a 24 hour block. Coffee // have a ☕️ // beans // 05:48, 2 February 2018 (UTC)
@Coffee: Cutting short talk-page discussions that are about whether something is in policy by unilaterally declaring that they are not, because you say so and that anyone who disagrees will get blocked, does not meet my definition of sanity, nor Wikipedia's definition of an administrator's remit. Back down before you hurt yourself. —David Eppstein (talk) 05:54, 2 February 2018 (UTC)
I'm not in any way playing with you David. Even the slightest inkling of an edit that breaks WP:ARBAP2 or WP:BLPDS and you're getting blocked just like anyone else on this site... but then because you're a sysop you're also going to be explaining yourself to ArbCom the day after tomorrow in the largest case I've ever seen, or ever created (ARBAP3). Coffee // have a ☕️ // beans // 06:23, 2 February 2018 (UTC)
I'd say "bring it", because I'm not impressed by your bluster, but I think that would be bad advice. Again, back down before you hurt yourself more than your actions so far in this case already have. Leave it to someone uninvolved. You may feel that the thread is a problem, but it doesn't have to be your problem. You are breaking the rules for how admins should behave (specifically WP:INVOLVED) and every step you take gets you deeper in. —David Eppstein (talk) 06:26, 2 February 2018 (UTC)
Acting as an administrator has not nor will it make me involved. Please read WP:UNINVOLVED for more information. Coffee // have a ☕️ // beans // 07:08, 2 February 2018 (UTC)
It's not the "Acting as an administrator", it's the "starting a discussion thread on a talk page and then participating in the discussion" that makes you involved. —David Eppstein (talk) 07:54, 2 February 2018 (UTC)

Therese Biedl

Hello - my edit on Therese Biedl created a valid external link to her profile at University of Waterloo. Your reversion of my edit restored a dead link. If you think there's a better valid URL for Ms. Biedl, then by all means change the link to that, but I believe her UW profile to be a good choice, and certainly better than the dead link you restored. Incidentally, I had a look and found her personal page, which is quite thin in terms of content and may not have been maintained for quite some time. I'm off doing the other work that I've been doing. Have a nice day, PKT(alk) 16:58, 6 February 2018 (UTC)

I did not simply restore the dead link. I found her correct home page address and used that instead. Her profile is a very formalized and static page created by her employer; it was already used as a reference, and is very different from her home page, a web page she created herself. It was incorrect to replace the url by the profile and still call it the home page. Also, "Ms." is the wrong term of address when referring to the professional accomplishments of an academic with a doctorate and a faculty position; try "Prof." or "Dr." —David Eppstein (talk) 17:47, 6 February 2018 (UTC)

Who knows what a topologist is?


Helen Frances Cullen (January 4, 1919 – August 25, 2007) was an American topologist.


Helen Frances Cullen (January 4, 1919 – August 25, 2007) was an American mathematician who did research in topology.

Generally I would try to write the opening of something like this in a way that would cause a typical lay reader to understand, after reading the first sentence, that it's about a mathematician. I don't think the first sentence above accomplishes that, so I changed it to the second. Michael Hardy (talk) 19:56, 14 February 2018 (UTC)

Well, except that by doing so you emphasized her research, which in this case is probably a mistake. She wrote a textbook in topology. She had to do some research to get there, but it is not what she is known for. —David Eppstein (talk) 19:58, 14 February 2018 (UTC)

Expert opinion, please?


DYK for Katherine Heinrich

Updated DYK query.svg On 18 February 2018, Did you know was updated with a fact from the article Katherine Heinrich, which you recently created, substantially expanded, or brought to good article status. The fact was ... that Australian mathematician Katherine Heinrich was the first female president of the Canadian Mathematical Society? The nomination discussion and review may be seen at Template:Did you know nominations/Katherine Heinrich. You are welcome to check how many page hits the article got while on the front page (here's how, Katherine Heinrich), and it may be added to the statistics page if the total is over 5,000. Finally, if you know of an interesting fact from another recently created article, then please feel free to suggest it on the Did you know talk page.

Gatoclass (talk) 00:03, 18 February 2018 (UTC)

Katherine Heinrich

I've kept the info and the source, just moved it in line with MOS. What's your problem? GiantSnowman 17:36, 18 February 2018 (UTC)

You're still paying attention to form only and not content. Making a whole section out of her birthplace is better than removing it altogether, but breaks the flow of the article. —David Eppstein (talk) 17:39, 18 February 2018 (UTC)
Then feel free to move it elsewhere. But it does not go in the opening brackets. GiantSnowman 17:43, 18 February 2018 (UTC)
I bet you're also one of those kind of people who also think the full dates of birth and death should always go in the first sentence, even though the MOS only actually states it should be somewhere in the lead and even in cases when all that parenthetical junk makes it very difficult for readers to find the actual content at the end of the sentence. —David Eppstein (talk) 17:48, 18 February 2018 (UTC)

DYK nomination of Annalisa Crannell

Symbol question.svg Hello! Your submission of Annalisa Crannell at the Did You Know nominations page has been reviewed, and some issues with it may need to be clarified. Please review the comment(s) underneath your nomination's entry and respond there as soon as possible. Thank you for contributing to Did You Know! Jo-Jo Eumerus (talk, contributions) 20:13, 18 February 2018 (UTC)

Merger discussion for Bayesian


An article that you have been involved in editing—Bayesian—has been proposed for merging with another article. If you are interested, please participate in the merger discussion. Thank you. Shhhnotsoloud (talk) 14:14, 20 February 2018 (UTC)

Women's History Month 2018 at Women in Red

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Welcome to Women in Red's March 2018 worldwide online editathons.
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Historically, our March event has been one of the biggest offerings of the year. This year, we are collaborating with two other wiki communities. Our article campaign is the official on-line/virtual node for Art+Feminism. Our image campaign supports the Whose Knowledge? initiative. Women's History Month 2018

Continuing: #1day1woman Global Initiative

(To subscribe: Women in Red/English language mailing list and Women in Red/international list. Unsubscribe: Women in Red/Opt-out list) --Rosiestep (talk) 16:08, 20 February 2018 (UTC) via MassMessaging

Your GA nomination of Prime number

The article Prime number you nominated as a good article has passed Symbol support vote.svg; see Talk:Prime number for comments about the article. Well done! If the article has not already been on the main page as an "In the news" or "Did you know" item, you can nominate it to appear in Did you know. Message delivered by Legobot, on behalf of Jakob.scholbach -- Jakob.scholbach (talk) 15:01, 23 February 2018 (UTC)

Thanks, Jakob.scholbach! That was a lot of work, even for a GA nom, but I think it was worth it. —David Eppstein (talk) 16:31, 23 February 2018 (UTC)
Scholarly Barnstar.png Scholarly Barnstar
I just wanted to chime in with a note of gratitude. Excellent work! XOR'easter (talk) 16:43, 23 February 2018 (UTC)
Thanks, and thanks for your work on the article as well. —David Eppstein (talk) 16:45, 23 February 2018 (UTC)

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