contour_plot defaults changed to fill, affects implicit_plot

[johnperry-math]

In Sage 3.1.1,

implicit_plot(x^2+y^2-1,(x,-1.1,1.1),(y,-1.1,1.1),plot_points=100).show(aspect_ratio=1)

produces a very nice circle.

In Sage 3.1.4, the same code produces a filled-in disc. Likewise, implicit_plot tries to fill in all curves;

implicit_plot(5*x^4-x^2-y^2,(x,-5,5),(y,-5,5))

looks odd.

The cause is contour_plot (called by implicit_plot): the default for the fill option is True. Feeding fill=False to implicit_plot produces the desired behavior:

implicit_plot(x^2+y^2-1,(x,-1.1,1.1),(y,-1.1,1.1),plot_points=100,fill=False).show(aspect_ratio=1)

Component: graphics

Issue created by migration from https://trac.sagemath.org/ticket/4462

[johnperry-math]

Attachment: circle_sage3.1.1.png

result of implicit_plot in sage 3.1.1

[johnperry-math]

result of implicit_plot in sage 3.1.4

[johnperry-math]

comment:1

Attachment: circle_sage3.1.4.png

The fix is easy: change line 2926 of site-packages/sage/plot/plot.py, which currently reads

@options(contours=(0,0))

to

@options(contours=(0,0),fill=False)

[jasongrout]

comment:2

It looks like #4201 forgot to override that option of contour plot. That's where the change was made.

I refereed that patch; my bad.

[jasongrout]

comment:3

Attachment: implicit-plot-no-fill.patch.gz

[jasongrout]

comment:4

John Perry should also receive credit for the patch, since he gave the actual fix in his comment. I added documentation as well.

[mwhansen]

comment:5

Looks good.

[sagetrac-mabshoff]

comment:6

Merged implicit-plot-no-fill.patch in Sage 3.2.rc0