William Stein wrote:
> On Tue, Oct 13, 2009 at 7:44 PM, Jason Grout
> <[email protected]> wrote:
>> kcrisman wrote:
>>>
>>> On Oct 13, 6:05 pm, "[email protected]" <[email protected]> wrote:
>>>> Hello all, is there any other possibility how to plot implicit
>>>> function than implicitplot?
>>>>
>>>> I do not like implicitplot too much, since it is in fact countourplot
>>>> and it is not easy to set the color (for example).
>>> There is not currently any other way to do this, I think. A colleague
>>> of mine has some experimental code to implicit plot the "right" way
>>> (by following derivatives around and spot-checking nearby to not miss
>>> components, I guess), but doesn't consider it ready for prime time
>>> yet.
>>
>> How do you do an implicit plot "right"? Scipy has tools for numerical
>> integration (you mention following derivatives), if that helps.
>
> I think what the user wants is to be able to *work with* contour plots
> in the same way one can work with normal plots. E.g., set the color.
> Right now they are always black, right? Etc.
Nope; but it's a pretty raw wrapper around the matplotlib functionality.
From the documentation of contour_plot (which is what implicit_plot
really is):
- ``cmap`` -- a colormap (default: ``'gray'``), the name of
a predefined colormap, a list of colors or an instance of a
matplotlib
Colormap. Type: ``import matplotlib.cm;
matplotlib.cm.datad.keys()``
for available colormap names.
We only have one cryptic example, though:
sage: f(x,y) = x^2 + y^2
sage: contour_plot(f, (-2, 2), (-2, 2), contours=2, cmap=[(1,0,0),
(0,1,0), (0,0,1)])
A clearer example would be:
sage: contour_plot(f, (-2, 2), (-2, 2), contours=3,fill=False,
cmap=["red", "green","blue"])
There is no mention of this in implicit_plot docs. However, here is an
example:
implicit_plot(x^2+y^2==1, (x,-2, 2), (y,-2, 2), cmap=["red"])
Mathematica doesn't have an implicitplot anymore, deprecating it for
CountourPlot, which now accepts equations. That's one way to unify the
two concepts.
Jason
--
Jason Grout
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