On 9/14/10 8:12 PM, kcrisman wrote:
On Sep 14, 3:00 pm, "D.C. Ernst"<ernst.tr...@gmail.com> wrote:
If I type the following into Sage (which is straight from the
implicit_plot documentation), I get a black square:
x,y=var('x,y')
f(x,y) = x^2 + y^2 - 2
implicit_plot(f, (-3, 3), (-3, 3),fill=True).show(aspect_ratio=1)
Of course, if you remove "fill=True", then everything works as
expected. The documentation should probably remove the "fill=True",
right?
Well, but it's supposed to demonstrate the fill option, which
* ``fill`` -- boolean (default: ``False``); if ``True``, fill
the
region f(x,y)< 0.
So perhaps there has been a regression - I get the same thing in both
4.5.3 and 4.3 (though in 4.3 I get a ghostly circle in the middle).
Not for the first time, we wish there were a way to do doctesting on
the image files produced...
sage: contour_plot(f, (-3, 3), (-3,
3),fill=True,contours=(0,0)).show(aspect_ratio=1)
doesn't do what we want either. In fact I'm having trouble getting
what I want with
sage: contour_plot(f, (-3, 3), (-3,
3),fill=True,contours=[0,0]).show(aspect_ratio=1)
sage: contour_plot(f, (-3, 3), (-3, 3),fill=True,contours=[-oo,
0]).show(aspect_ratio=1)
sage: contour_plot(f, (-3, 3), (-3,
3),fill=True,contours=[-1000,0]).show(aspect_ratio=1)
I'm not sure what happened here, because
sage: contour_plot(f, (-3, 3), (-3,
3),fill=True,contours=1).show(aspect_ratio=1)
doesn't give just one contour, either.
I can think of several people whose fault this could be, and I'm one
of them, but I'm not sure what's going on yet (albeit won't have time
to check it in detail now). Can you file a Trac ticket for this
issue, and cc: kcrisman and jason on it?
Already done: http://trac.sagemath.org/sage_trac/ticket/9744
I wrote some rough code fixing it about a month ago. Volunteers to
finish it and polish it are welcome!
Jason
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