User talk:Fredrik Johansson

Tasks: start a new article • add basic, wanted or requested articles • add definitions • add metadata • edit new pages

Welcome to the Citizendium! We hope you will contribute boldly and well. Here are pointers for a quick start, and see Getting Started for other helpful "startup" links, our help system and CZ:Home for the top menu of community pages. You can test out editing in the sandbox if you'd like. If you need help to get going, the forum is one option. That's also where we discuss policy and proposals. You can ask any user or the editors for help, too. Just put a note on their "talk" page. Again, welcome and have fun! Robert Tito 15:38, 30 January 2007 (CST)

Recently uploaded image(s)

Hi Fredrik. Thanks for contributing to CZ! Do me a favor and place licensing data at the image page of yourself you recently uploaded. See Images Help—Copyrights for help. Thanks! — Stephen Ewen 23:03, 6 April 2007 (CDT)

Oops, that was supposed to have been there. Fredrik Johansson 03:37, 7 April 2007 (CDT)

math style

Hi! I've just come upon your user page. The passage concerning your views on mathematical style (making the difficult accessible) looks particularly interesting. Would you consider writing a paragraph along these lines on the Math Workgroup page? --AlekStos 03:22, 10 April 2007 (CDT)

Hi Alek. I might give it a shot. Fredrik Johansson 07:24, 10 April 2007 (CDT)

CSS problem

Email bugs@citizendium.org about that. —–Stephen Ewen 22:03, 10 April 2007 (CDT)

Great job

I just wanted to let you know that you've been doing a superb job with the mathematics articles. Keep up the good work! :) --Joshua David Williams 14:58, 12 April 2007 (CDT)

Thanks. I'll try to keep up to the extent my free time permits. Fredrik Johansson 15:17, 12 April 2007 (CDT)

gamma

Hi, I guess I have the requested article on Euler's gamma. Please contact me, my account is alex2cf _at_ gmail_ (dot_com) -- if you are still interested in :-) --AlekStos 02:42, 21 April 2007 (CDT)

Thanks for the graph!!

Wow -- thanks for the graph at logarithm! It looks great! I just wrote the article a few hours ago and now it has a colour graph!! And thanks for the markup edits, too. This is one of the great things about working on a wiki, when other people respond and synergistic collaboration happens. I wonder whether I could do graphs ... what formats are possible? How do you upload them? Re 1/x: I mean "integral", of course.  :-) --Catherine Woodgold 18:16, 28 April 2007 (CDT)

Thank you :-) You can upload files at Special:Upload. There are a number of supported formats, but PNG is best for graphs. Fredrik Johansson 18:19, 28 April 2007 (CDT)

Really good-looking and "user-friendly". Good work! However, there is a little something that bothers me - a part of log_10 (x) graph looks like a straight vertical line. Could we avoid it? Actually, you know well that a vertical line does not represent a function :) Did you know, however, that in some universities/high schools such an inaccuracy is particularly "condemned"? So maybe just using a thiner line would do? I'm sure you can find a not-much-time-consuming solution. :)

BTW, what do you use to generate your graphs? You mentioned a "script" and that was intriguing.--Aleksander Stos 12:09, 26 May 2007 (CDT)

You speak Python, right? I mostly use Matplotlib and occasionally PyX (which is very buggy and poorly documented, however).

Here's the Matplotlib script I used to generate the logarithm graph:

from __future__ import division
from pylab import *
rc('text', usetex=True)
figure(figsize=(5,4))

xmin, xmax, ymin, ymax = -0.5, 5.0, -3.0, 3.0

x = arange(xmin, xmax, 0.01)
y1 = log(x)
y2 = log(x) / log(10)
y3 = log(x) / log(2)

axhline(label=None, color='#000000')
axvline(label=None, color='#000000')

p1 = plot(x, y1, '-', color='#006688', lw=1.8)
p2 = plot(x, y2, '-', color='#6600aa', lw=1.8)
p3 = plot(x, y3, '-', color='#ff6600', lw=1.8)

axis([xmin, xmax, ymin, ymax])

xlabel('$x$ ', fontsize=16)
ylabel('$y$', fontsize=16)

xticks(range(6), [str(i) for i in range(6)])
yticks(range(-3,4), [(" " + "$" + str(i) + "$") for i in range(-3,4)])

text(2.4,1.8, r"$y = \mathrm{log}_2(x) $", fontsize=12)
text(3,0.83, r"$y = \mathrm{ln}(x)$", fontsize=12)
text(3.5,0.2, r"$y = \mathrm{log}_{10}(x)$", fontsize=12)

legend((p3, p1, p2), ("Base-2 logarithm", "Natural logarithm",
    "Base-10 logarithm"), loc='lower right')

savefig('logarithms.png')

Regarding your issue with the graph, I think the best solution is to explain the asymptotic behavior in the text. Fredrik Johansson 12:36, 26 May 2007 (CDT)

Thanks a lot! --Aleksander Stos 04:45, 31 May 2007 (CDT)

Thank you for your corrections!

I was terribly respectless with the details in resistor. Luckily you checked it through. --Magnus Sundell 15:31, 4 May 2007 (CDT)

Newton's Method

Could you check this edit, please? I assume that his comment is incorrect and that you created that image on your own. It looks like a pretty standard representation of Newton's method to me.

It's obviously not a big issue, since you both released your works into the public domain, but we should try to be accurate if possible.--Joe Quick (Talk) 15:19, 19 May 2007 (CDT)

The similarity is a coincidence. I knew there was an illustration on Wikipedia, but I avoided looking at it before drawing the image to avoid this. I don't claim to have come up with the original concept, but nor did Oleg; I have seen dozens of illustrations of Newton's method that all look the same: x axis, some convex function, tangent line, dashed line between (x_0, 0) and (x_0, f(x_0)). Check for example Heath (in the references for the article).

If the proportions of these two are similar, that's because they happen to look good. I did not draw the image by hand; I generated it from a script in which I adjusted the numerical values until the result looked good, without comparing to any external image. Fredrik Johansson 15:34, 19 May 2007 (CDT)

That's just what I thought probably happened. :) I'll remove the inaccurate disclaimer. --Joe Quick (Talk) 01:56, 21 May 2007 (CDT)

I am going around throwing illustration of plagiarism, sorry about that, that was a bad idea on my part.

Yet, the reason for my original note on the image page was the surprise at how similar the images actually look after one of them is by shrank a bit the same in all directions and translated onto the other one. I posted a comparison here, with Fredrick's image in blank and my own in red. Funny to see. Oleg Alexandrov 16:53, 23 May 2007 (CDT)

No problem Oleg. After seeing that comparison, I'm having trouble believing my own word :-) If you're interested, my function is y = exp((x+2.5)/2)/2 - 3 and x0 = 3. - Fredrik Johansson 17:05, 23 May 2007 (CDT)

Mine is exp(x)/1.5-0.5 and x0=0.7. That both of use chose to use an exponential with similar scalings and tweaks, shows, as they say, that "Great Minds Think Alike". :) Oleg Alexandrov 18:17, 23 May 2007 (CDT)

The Discordianism article

I wanna thank you for fixing the formatting on that thumb. I know it may seem a small thing, but I'm new to authoring articles from whole cloth, and every tiny bit helps. As you're the first person besides me to do even a minor edit to that article, figured I'd give you a shout out on it, and thank you. Take care. Michael MacNeil 09:31, 23 May 2007 (CDT)

Comments spot on

Hi Fredrik!

Read the comments on your user page with interest. I must say I completely agree with your views on stability--or rather, the lack thereof--over at WP. Have a question, though: what is "scopecreep"?

May I shamelessly plagiarize your comments for my own userpage? With credit where it's due, of course! ;)

Aleta Curry 19:53, 12 June 2007 (CDT)

Scope creep would be the accumulation of trivia, detailed coverage of minority views, and so on. Feel free to copy anything you like, and thanks! Fredrik Johansson 20:00, 12 June 2007 (CDT)

Gamma function

I left some questions on Talk:Gamma function and you are probably the person to answer them. You may also want to go over the changes I made to the article, especially the first two, to see whether I didn't mess something up. It's time that we get another approved article! -- Jitse Niesen 05:49, 25 August 2007 (CDT)

Spherical harmonics

Hi Fredrik, some time ago you commented that the article spherical harmonics could do with some drawings. I would appreciate it if you have any suggestions for some illustrations (or even better: if you yourself could add some drawings to the article). Thank you. --Paul Wormer 07:37, 2 September 2007 (CDT)