I just tested the following:
plot(arrow((-0.03,-0.03),(6,6)))
which "corrects" the problem and makes it seem as if the arrow
actually starts from (0,0).
Is this intended?
On 8 Nov., 23:46, Karsten <karste...@gmail.com> wrote:
> Thanks! This corrects plotting the sine and cosine functions.
> But there is no difference when plotting arrows, except the fuzzier
> axes you mentioned.
> Any ideas about that one?
>
> I really prefer plotting to look as it should with fuzzier axes since
> otherwise sage can not be used to present graphs for other people.
>
> On 8 Nov., 19:37, Jason Grout <jason-s...@creativetrax.com> wrote:
>
>
>
>
>
>
>
> > On 11/8/10 5:00 PM, Karsten wrote:
>
> > > I am a beginner using sage, and I have encountered a problem using the
> > > plot function. Plotting a simple sine or cosine function is not very
> > > precise:
>
> > > t=var('t')
> > > v=plot(sin(t),-pi,pi
>
> > > The function is clearly positive in t=-pi, where it should be zero.
> > > The mistake becomes even more clear when setting line thickness to 99:
>
> > > t=var('t')
> > > v=plot(sin(t),-pi,pi,thickness=99)
>
> > > In this case when x=0 the line is crossing 1 in the upper side and not
> > > -1 in the lower side.
>
> > > This problem occurs in all functions i have encountered so far, as if
> > > the function is displayed 1 or 2 pixels off. It's even worse when
> > > plotting arrows:
>
> > > plot(arrow((0,0), (2,3)))
>
> > > Here the arrow is clearly not starting in (0,0) as it should.
>
> > > Is there a solution for this kind of problem?
>
> > Yes. It's a tradeoff between sharper graphics and rounding issues with
> > pixels in plots. IIRC, the basic issue is that horizontal and vertical
> > lines are "snapped" to the nearest pixel, so that they aren't
> > anti-aliased and fuzzy.
>
> > This has been investigated quite a bit at:
>
> >http://trac.sagemath.org/sage_trac/ticket/7808
>
> > In short, you can do:
>
> > import matplotlib
> > matplotlib.rcParams['path.snap'] = False
>
> > This will make horizontal and vertical lines (like the axes) not snap to
> > the nearest pixel. Things may be a bit fuzzier, though.
>
> > Thanks,
>
> > Jason
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