In Sage notebook v 4.6.1 I wrote:
var('theta')
polar_plot((1/sin(theta)),(theta, pi/12, pi/2))
I got
libpng error: Image width or height is zero in IHDR
Traceback (click to the left of this block for traceback)
...
RuntimeError: Error building image
What am I doing wrong?
Thanks for the trac ticket.
Here is another one with a problem:
polar_plot(3*sqrt(cos(2*theta)),(theta, 0, 2*pi))
gives the follow graph:
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> Sorry, file uploading requires karma > 60
Arrrgh!
Well, ok try it yourslf. On my v.4.6.1 worksheet I see a plot with some weird discontinuity near the origin.
Ok, yes with this option I do get a reasonable looking graph but I also get the message: verbose 0 (3998: plot.py, generate_plot_points) WARNING: When plotting, failed to evaluate function at 24999 points. verbose 0 (3998: plot.py, generate_plot_points) Last error message: ''
Yeah, but that's ok. I mean, you should have gotten that error for the one without the `plot_points` option set as well. That is because you are plugging in `theta` that give you a negative number inside the square root :) and plot ignores them but tells you that some of its points did that.
I don't get an error, but I do get plots that are very stretched out. Even with
polar_plot((1/sin(theta)),(theta, pi/12, pi/2),aspect_ratio='auto')
the y-axis isn't as nice as when we do
plot(1,(x,0,3))
I am running 4.7.2 alpha3, I think. What version are you running?
This isn't a full answer, but I think that there is something wrong with how we are doing the axes for polar plot - probably because of our aspect ratio handling (?).
Compare
sage: polar_plot(1/sin(1.01*theta),(theta, pi/12,pi/2))
with
sage: polar_plot(1/sin(1.001*theta),(theta, pi/12,pi/2))
and you'll see what I mean.
This is now Ticket 11978.
Asked: 2011-11-01 20:57:13 +0200
Seen: 765 times
Last updated: Nov 04 '11
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