Cffk

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Hello, Cffk, and welcome to Wikipedia! Thank you for your contributions. I hope you like the place and decide to stay. Here are some pages that you might find helpful:

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Reverts

I reverted a couple of your edits that promote your own recent work, per WP:COI. If these are appropriate to include in the articles, the best way to get there is to propose the info on the respective article talk pages, and let non-conflicted editors decide what to say about it. Dicklyon (talk) 04:16, 23 February 2011 (UTC)

Re: Clenshaw algorithm

Thanks, but I had fixed those, and found a bunch more (that I didn't create), which took me a while... edit conflict, arrgh! 71.41.210.146 (talk) 18:47, 16 July 2013 (UTC)

Okay, now if you'd like to have a look and fix anything that annoys you. I spent a while trying to get the equations from various sources to work properly, ending up flipping the sign convention on α and β to match Numerical Recipes. Another citation maybe you can work in: 3: Chebyshev Expansions or "Numerical Methods for Special functions" 71.41.210.146 (talk) 18:53, 16 July 2013 (UTC)

Can't the last equation in the Horner section be written S(x) = b_0. (Also 1_0 -> a_0?) cffk (talk) 18:57, 16 July 2013 (UTC)

Thanks! Some things are so much easier for other people to see. I didn't mention $b_{0}$ in the Horner section because the general case doesn't take the recurrence that far, and this is a simple application example, not an "optimal implementation" discussion. (In the Chebyshev case, things are different.) But I'll accede to your opinion. 71.41.210.146 (talk) 02:01, 17 July 2013 (UTC)

Thanks for the correction to the subsection title (I had "geodetic" on the brain), and the wonderful example using matrix math in the first place! I hope I didn't damage your text too badly. :-) 71.41.210.146 (talk) 23:01, 16 November 2014 (UTC)

No, this is fine. I'm glad that you checked it and that you found it useful. cffk (talk) 04:19, 17 November 2014 (UTC)

Junk references

Hey, your link removal at great_circle to this http://www.distance-calculator.co.uk - hardly junk old chap, has lots of useful tools and references and does use the haversine formulae and was an example of a site that used it so was actually pertinent to the discussion as it does use great circle type calculations to arrive at its distances. Before you decided to remove it, it was there for years! Your call of course, but please think carefully the next time you decide to remove someones work, especially if you want to call it junk. :)

(NotMrOllie (talk) 13:47, 31 July 2013 (UTC))

The link, when I follow it, sure looks like junk. By this I mean awful cluttered and confusing layout, ads, requests to divulge your location and to login, not easy to navigate, etc.; altogether a real turn-off. It looks like a site that survives by selling ads and wants to use Wikipedia to drive traffic to it. Wikipedia is much better off not including such links. If you have anything to do with this site, you should regard this as potentially useful user feedback. cffk (talk) 14:15, 31 July 2013 (UTC)

That site's been around for 10 years and has lots of repeat visitors and actually gets thank you emails daily. It only asks for your location if you want to find out where you are going to and explicitly click on a location based link, otherwise there's no enforced requests. You are of course, entitled to your opinion. Every site on the web needs to make money, even wikipedia, it's called Capitalism! Thankfully, wikipedia doesn't entirely care or rely on subjective opinions. It's a concern if totally subjective views like yours are used as a defining criteria for removing links to websites. I just ask that you think about general use to others before you take such actions in future and consider that many hobby type sites have been developed that look less than pleasing on the eye or fit to a standard definition of some idea of perfect navigation - the web isn't a beauty contest. Usually, folks vote with their feet.

In any case, thanks for your pov!

Two questions

I am writing a new article, User:Cffk/sandbox/Geodesics on an ellipsoid, and two questions come up:

1. I switched to MathJax several months ago and am now shocked at how awful the default math rendering is. So (a) how about making MathJax the default renderer? (b) if not, how can a user without a wikipedia account view the math using MathJax?
2. I use <div class="references-small"> for my reference section (where I've placed all my references instead of sprinkling them throughout the article) and yet the references appear in the standard font size. What am I doing wrong?

1. If you want to propose MathJax to become the default renderer, the place to do so would probably be WP:Village pump (technical). I don't think there's a way for non-registered users to change their preferences and use MathJax.
2. I have changed that to <div class="reflist">. However, you really should "sprinkle" your references throughout the article to clarify which source supports which statement. See WP:Referencing for beginners on how to do so, or just use <ref>...</ref> tags. Huon (talk) 00:14, 6 August 2013 (UTC)

Thanks. I do, of course, cite the references within the text using { { harv|Name|year } }. cffk (talk) 01:06, 6 August 2013 (UTC)

Separated at birth?

Are you really Dr. House, incognito? He is also from Princeton! Come on, really, this is you, right? LOL :) (talk) 02:36, 1 September 2013 (UTC)

This edit summary doesn't make sense: What is there without the errors bounds is _not_ a statement of a theorem. Michael Hardy (talk) 22:21, 8 September 2013 (UTC)

See response on Talk page for article... cffk (talk) 12:10, 9 September 2013 (UTC)

about the ellipsoid surface

great effort. and I want to see Riemann curvature tensor and Ricci tensor. and how are they related to the geodesics equation. I think you can do it. Unfortunately, I am not able to do it. Jackzhp (talk) 04:34, 27 November 2013 (UTC)

See my answer on the talk page. cffk (talk) 13:03, 27 November 2013 (UTC)

Your GA nomination of Geodesics on an ellipsoid

Hi there, I'm pleased to inform you that I've begun reviewing the article Geodesics on an ellipsoid you nominated for GA-status according to the criteria. 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 Turnitinpro -- Turnitinpro (talk) 01:52, 6 December 2013 (UTC)

Your GA nomination of Geodesics on an ellipsoid

The article Geodesics on an ellipsoid you nominated as a good article has failed ; see Talk:Geodesics on an ellipsoid for reasons why the nomination failed. If or when these points have been taken care of, you may apply for a new nomination of the article. Message delivered by Legobot, on behalf of Turnitinpro -- Turnitinpro (talk) 05:42, 13 December 2013 (UTC)

I don't understand why the MathJax disclaimer on the Spherical trigonometry exists.

You reverted my edit on removing a reminder to use MathJax on the Spherical trigonometry article.

I simply don't understand why the reminder should exist. No other math article has it! And the math articles that use similar math code on WP don't have these notices.

Besides, the disclaimer looks like a blemish amongst the text. Hill Crest's WikiLaser! (BOOM!) 04:13, 13 March 2014 (UTC)

To answer your question "why the reminder should exist": many people aren't aware how much better mathematics is rendered with Mathjax. This particular article looks incredibly clunky with the default PNG rendering. User:Peter Mercator did a lot of work cleaning up this article. He put this recommendation in and I would be inclined to go along. I guess I could ask you "what's the harm in leaving it in?" I don't feel that strongly about whether this recommendation stays or not. On the other hand, I do think that editors should defer, where possible, to the wishes of the major contributors to articles. I've asked Peter to comment. cffk (talk) 22:09, 12 March 2014 (UTC)

I see the point there... But I believe that the disclaimer looks nicer on a template rather than blended with the text or blaring out "CAUTION; MATHJAX IS RECOMMENDED TO VIEW PAGE; IF YOU HAVE VIEWING PROBLEMS, ENABLE MATHJAX" Hill Crest's WikiLaser! (BOOM!) 04:15, 13 March 2014 (UTC)

I added the comment because so many readers are ignorant of MathJax and I much prefer to leave the comment as it is because Wiki banners are really unpleasantly intrusive at the head of a page. My comment isn't particularly unsightly but I accept that this may not be the best way of tackling this problem. I would never recommend Hillcrest's caution in CAPITALS. I also agree that no maths pages carry such a comment but perhaps they should!  Peter Mercator (talk) 23:22, 14 March 2014 (UTC)

I mean, a template similar to the "Contains Japanese text" template. And the all caps thing wasn't a suggestion. Like, it should say "This article contains math code. This article is best viewed with MathJax." Hill Crest's WikiLaser! (BOOM!) 19:22, 17 March 2014 (UTC)

Does such a template exist? If not, this is something you might pursue in Mathjax discussion forum. (My vote is just to make Mathjax the default rendering scheme. However I realize that this might not be feasible.) cffk (talk) 19:55, 17 March 2014 (UTC)

OER inquiry

Hi Cffk, I'm sending you this message because you're one of about 300 users who have recently edited an article in the umbrella category of open educational resources (OER) (or open education). In evaluating several projects we've been working on (e.g. the WIKISOO course and WikiProject Open), my colleague Pete Forsyth and I have wondered who chooses to edit OER-related articles and why. Regardless of whether you've taken the WIKISOO course yourself - and/or never even heard the term OER before - we'd be extremely grateful for your participation in this brief, anonymous survey before 27 April. No personal data is being collected. If you have any ideas or questions, please get in touch. My talk page awaits. Thanks for your support! - Sara FB (talk) 20:37, 23 April 2014 (UTC)

cite doi disappearing in the PDF version of article

Please check out User:cffk/Meridian arc where I'm updating the main article on this subject. I use constructions like

In 1837, [[Friedrich Bessel|Bessel]] obtained one such series,<ref>{{cite doi
|10.1002/asna.18370142301
|comment = Bessel 1837
|noedit
}}</ref> which was put into a simpler form by ...

This works fine in the resulting article; the reference is cited as a superscript and the DOI citation is given in the list of reference. However, if I "Download as PDF" the article, the citation and the reference have completely evaporated. (See, for example, the last two references in the article.) What happened? Is there some way to refer to cite-doi articles which allows the reference to appear in the PDF version. Thanks! cffk (talk) 17:37, 11 September 2014 (UTC)

I checked several articles and they all behave this way. I'll leave the {{help me}} template on here in case someone else has a better answer, but it seems like it is functioning normally. —    Bill W.    (Talk)  (Contrib)  (User:Wtwilson3)  — 19:39, 11 September 2014 (UTC)

Hi Cffk. First off, I fixed a few of the ref tags in your article, they were in odd places. Second, while I don't have a solution to your issue my best guess is that a bot fills out the {{cite doi}} information and the PDF creator does not have access to that bot. Thus, it doesn't treat it as a reference and ignores it. My suggestion would be to use the subst tag at the beginning of the reference (e.g. {{subst:cite doi|etc}}), which will create an actual journal reference which will (if my theory is correct) be readable by the PDF creator. If this does indeed do the trick, change your {{help me}} to {{help me-helped}}._{(this doesn't work; I tested it)} Otherwise, I'm sure someone more knowledgeable than I will be able to assist . Primefac (talk) 19:45, 11 September 2014 (UTC)

Thanks, both of you, for your help. It looks like the problem may just be a defect in the way the PDF creator works. (However I note that the citations in Geodesics on an ellipsoid, which depends heavily on cite-doi but uses Harvard-style references, come out find in the PDF.) I'll wait a day or two in case someone can figure out how to coax the PDF creator into doing the right thing. cffk (talk) 19:59, 11 September 2014 (UTC)

The question I have now is, "Who handles the PDF creation process?" Anyone know where to look that up? —    Bill W.    (Talk)  (Contrib)  (User:Wtwilson3)  — 21:41, 11 September 2014 (UTC)

I'd probably ask at WP:Village pump (technical). Some other steps you may want to try: What happens if you add something beyond the {{cite doi}} to the footnote, say <ref>See: {{cite doi|...}}</ref>? Does that produce a footnote whose only content is "See:"? If that still doesn't produce any footnote, the problem is more than just the citation template. If {{cite doi}} is the issue, as a possible workaround you can look up the bot-created reference page (Template:Cite doi/10.1002.2Fasna.18370142301) and copy-paste the reference into the article, avoiding that citation template altogether. Huon (talk) 23:33, 11 September 2014 (UTC)

Mathjax stalls loading GreekAndCoptic.js

I have Mathjax turned on by default and generally this works great. However on some pages (an example is great-circle distance), the Mathjax generation stalls with "Loading [MathJax]/jax/output/SVG/fonts/TeX/Main/Regular/GreekAndCoptic.js" and I am left looking as crufty PNG renderings of the math. The problem seems to be platform specific (I'm using Firefox under Linux) and I have seen similar miscellaneous complaints on the web. The following paragraph triggers the problem with this talk page (and the problem goes away if the Delta is changed to delta). I would be really nice to know what is going on here and how to avoid the problem.

On computer systems $\Delta$ done.

Thanks! cffk (talk) 15:20, 12 September 2014 (UTC)

May I suggest posting over on WP:VPT about this, as you will likely get a more productive response? --Mdann52talk to me! 16:29, 12 September 2014 (UTC)

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Equations on length of a degree of parallel / meridian on given latitude

I reverted your revert back, because your statement is simply not correct. You cannot left the minus sign just because it is on denominator. Eg. for parallel and ψ = 45° the denominator (1-e^2*sin^2ψ)^2/3 results approx. 0,994983419, but the correct value is around 1,005041874, which corresponds to (1-e^2*sin^2ψ)^-2/3; The table on the right is therefore not consistent with the equations on the left. Please check your math again and make some computations by hand before rejecting someone else's corrections. I think this will be better for everyone. Sincerely Coniotheca (talk) 15:11, 6 July 2016 (UTC)

I'm at a loss to understand your reasoning. I verified that the formulas in the current revision https://en.wikipedia.org/w/index.php?title=Latitude&oldid=728290447#Length_of_a_degree_of_latitude are consistent with the tabulated results. With your edit, they are not! cffk (talk) 15:33, 6 July 2016 (UTC)

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Inlinetext

Hi Cffk. I have always "assumed good faith" with other Wikipedia editors until encountering Inlinetext. There was a user back in August 2016 where I "assumed good faith" (PseudoScientist) and it just ended up being a big waste of time because the user was LTA/troll/disruptive. Inlinetext is acting just like PseudoScientist by attacking the user (Friyman) who reverted his first deletion on "Geodesics on an ellipsoid" and also accusing you of copyright violation and original research and "hoax". I don't want to waste more time again with someone (Inlinetext) who is clearly LTA/troll/disruptive, so I'm not going to attempt "discussion" with Inlinetext on the article talk page. Regards, Jrheller1 (talk) 22:28, 31 January 2017 (UTC)

Just noticed something. It looks like Inlinetext may be banned user Turnitinpro (the GA reviewer for "Geodesics on an ellipsoid"). Turnitinpro was part of the "India Against Corruption" sock-meatfarm as was Crapscourge (see [1]). Jrheller1 (talk) 05:53, 1 February 2017 (UTC)

Yes, I wondered the same thing. I'm not sure how a concrete case can be made for this, though. cffk (talk) 09:45, 1 February 2017 (UTC)

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Well done on the Ellipse page

I just wanted to say "well done" in regard to your discussion on the Ellipse page. I know it is a lot of work to be so thorough, but other editors do appreciate it. I was involved in previous discussions on the same general subject two years ago, and I'm glad you and a couple of other editors are taking the time to keep the article at good standards. Also I learned something about the Carlson algorithm from your Python code -- not sure I'll ever need to use it, but it is interesting :). LaurentianShield (talk) 23:24, 26 September 2018 (UTC)

@LaurentianShield: Thanks! I'm not sure how adept you are with python; in reading the code you need to be aware how the parallel assignments work, namely x, y = a, b evaluates a and b before doing either of the assignments. This makes the coding of the AGM very simple. cffk (talk) 00:15, 27 September 2018 (UTC)

Adlaj again

Hi Cffk, someone, possibly a sockpuppet but I have no hard evidence, is trying to reinsert the Adlaj paper as a reference, this time in the Sine article. I reverted based on the discussion you had with an IP on the Talk:Ellipse page. I may have been too hasty in my revert, so I was wondering if you could give the Sine article a glance and correct me if I was mistaken. Thanks. --Bill Cherowitzo (talk) 20:38, 10 November 2018 (UTC)

@Wcherowi: Thanks for the heads up. I've started watching this page. cffk (talk) 19:24, 12 November 2018 (UTC)

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source code for images on Geodesics on an ellipsoid

Howdy! Thanks for your wonderful work on that page and for creating geographiclib. I read your preprint on arxiv, too.

I was wondering if you'd be willing to share the code that was used to generate those images. (Or have you already shared them somewhere?) I was particularly interested in File:Envelope_of_geodesics_on_an_oblate_ellipsoid.svg.

Thanks for any help you can provide! cheers, 136.49.93.101 (talk) 21:40, 22 November 2018 (UTC)

Here you go. This requires that you have Matlab Central package 50605 installed.

envelope.m

globals;
printp=true;
xsize=4*0.66;ysize=4*0.66;
name='geod-envelope';

figure(1); initplot;

a = 1;
r = 10;
ell = [a, flat2ecc(1/r)];
lat1=-30;
lon1=0;
lat0=-lat1;lon0=180;
hold off;
for azi1=[-180:3:180],
  [lat,lon] = geodreckon(lat1,lon1,[120:2:240]',azi1,ell,1);
  xyz=proj([lat,lon],lat0,lon0,a,r);
  xyf=frontx(xyz);
  plot(xyf(:,1),xyf(:,2),'-','LineWidth',thin,'Color',0.3*blue+0.7*white);
  if azi1 == -180,
    hold on;
  end
end

[latc,lonc,~, ~, ~, ~, ~, s12c] = geodreckon(lat1,lon1,180,90,ell,1);
loncut=180+[-8:8]'/8*(180-lonc);
latcut=latc+0*loncut;
xyz=proj([latcut,loncut],lat0,lon0,a,r);
xyf=frontx(xyz);
plot(xyf(:,1),xyf(:,2),'-','LineWidth',thick,'Color',red);
s12d = geoddistance(lat1,lon1,-lat1,lon1+180,ell);
ds=(s12d-s12c)/2;
for s=[0:6],
  s12=s12c+ds*s;
  [lat,lon] = geodreckon(lat1,lon1,s12,[-180:2:180]',ell);
  xyz=proj([lat,lon],lat0,lon0,a,r);
  xyf=frontx(xyz);
  plot(xyf(:,1),xyf(:,2),'-','Color',green);
end

hold off;

axis image;
axis(0.25*[-1,1,-1.109,0.891]);
axis off;
printplot;

globals.m

global thick thin printp xsize ysize name red blue green white black;
thick=1;
thin=0.3;
red=[179,27,27]/255;
white=[1,1,1];
black=[0,0,0];
blue=[0,19,56]/100;
green=[9,45,27]/100;

initplot.m

function initplot(suffix)
global xsize ysize;
clf reset;
set(gcf,'Units','pixels');
set(gcf,'Position',100+120*[0 0 xsize ysize]);
set(gcf,'Units','normalized');
end

printplot.m

function printplot(suffix)
global xsize ysize name printp;
if printp,
  if nargin < 1,
    suffix = '';
  end
  set(gcf,'PaperSize',[xsize ysize]);
  set(gcf,'PaperPosition',[0 0 xsize ysize]);
%  print('-dpdf', [name suffix '.pdf']);
  plot2svg([name suffix '.svg']);
  system(['./trim.sh ' name suffix '.svg']);
end

frontx.m

function xy = frontx(xyz),
  c=xyz(:,3)>=-0.01;
  c=1+0./c;
  xy = [xyz(:,1).*c, xyz(:,2).*c];
end

proj.m

function xyz = proj(ll, lat0, lon0, a, f)
  %proj convert ll to ortho from pov of lat0 lon0
  if f>1
    f=1/f;
  end
  e2=f*(2-f);
  e2m=(1-f)^2;
  degree=pi/180;
  phi=[ll(:,1);lat0]*degree;
  lam=[ll(:,2);lon0]*degree;
  sphi=sin(phi);
  cphi=cos(phi);
  n = a ./ sqrt(1 - e2 * sphi.^2);
  slam = sin(lam);
  clam = cos(lam);
  z = e2m * n .* sphi;
  x = n .* cphi;
  y = x .* slam;
  x = x .* clam;
  east0 = [-slam(end)          ;  clam(end)          ; 0        ];
  north0 =[-clam(end)*sphi(end); -slam(end)*sphi(end); cphi(end)];
  up  =   [ clam    .*cphi     ,  slam    .*cphi     , sphi     ];
  up0 =   up(end,:)';

  pts = [x(1:end-1)-x(end), y(1:end-1)-y(end), z(1:end-1)-z(end)];
  x = pts * east0;
  y = pts * north0;
  z = up(1:end-1,:) * up0;
  xyz = [x, y, z];
end

trim.sh

#! /bin/sh
# Trim white space around plot2svg output to 10 units
file=$1
desc=`basename $1 .svg`
date=`date "+%Y-%m-%dT%H:%M%z"`
set -- `grep -1 '<clipPath ' $file | tail -1 | tr -s '[<>/a-z="]' ' ' |
awk 'BEGIN{w=10;}{printf "%.3f %.3f %.3f %.3f", $1-w, $2-w, $3+2*w, $4+2*w;}'`
mv $file ${file}~
sed -e "s/viewBox=\"[^\"]*\"/viewBox=\"$1 $2 $3 $4\"/" \
    -e "s/^  <rect x=.* fill=/  <rect x=\"$1\" y=\"$2\" width=\"$3\" height=\"$4\" fill=/" \
    -e "s%<desc>.*</desc>%<desc>Matlab/PLOT2SVG figure: $desc ($date)</desc>%" \
    ${file}~ > $file

cffk (talk) 13:46, 25 November 2018 (UTC)

You've got (off-wiki) mail

Hi – I mailed you on your personal account. Cheers DBaK (talk) 19:34, 26 November 2018 (UTC)

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Geodesics and local minimization

I reverted your edit on geodesics on an ellipsoid. I did not understand which claim of local minimality you were saying is incorrect and am posting here as it allows for easier discussion (if you still disagree with the contents) than in the edit explanation field. What I meant to convey in the text of the article is that locally, i.e., in a neighborhood of each point in the interval parametrizing the geodesic, the geodesic is a shortest path between (the images of) any two of the points in the neighborhood. 73.89.25.252 (talk) 19:07, 25 September 2020 (UTC)

@73.89.25.252: The claim that "the geodesic is a local minimum of path length among nearby paths" is false. Here's a counter example: On a sphere the equatorial path from longitude = -135d to 135d via longitude = 0d is a geodesic. However the nearby path consisting of the geodesic between (lat,long) = (0,-135) to (0.0001,0) connected to the geodesic from (0.0001,0) to (0,135) is shorter. (You can make 0.0001 as small as you like to satisfy "nearby".) cffk (talk) 19:48, 25 September 2020 (UTC)

OK. It can say local "stationary point" rather than "minimum" among nearby paths (at least for Riemannian closed manifolds) to accomodate this, but something more in the spirit of shortest paths would be that a geodesic (as a parametric curve) is a union (ie, gluing along open intervals) of strict geodesics (i.e., parametrized paths all of which are globally-shortest paths between any two of their points). This should work at least for Riemannian manifolds. 73.89.25.252 (talk) 23:46, 25 September 2020 (UTC)

I removed the phrase about "nearby paths". I did not see an obvious place to reintroduce it with a longer discussion, and the complications around critical points belong in a different article such as geodesic or Morse theory, so I deleted it rather than try to elaborate. Thanks for your comments. 73.89.25.252 (talk) 04:09, 26 September 2020 (UTC)

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