#13246: Automatic exclusion of non-domain points in things like arcsec
-------------------------------------+-------------------------------------
Reporter: kcrisman | Owner: jason, was
Type: defect | Status: needs_review
Priority: major | Milestone: sage-6.3
Component: graphics | Resolution:
Keywords: | Merged in:
Authors: Punarbasu | Reviewers: Ralf Stephan, Karl-
Purkayastha | Dieter Crisman
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/ppurka/automatic_exclusion_of_non_domain_points_in_things_like_arcsec|
a01095ea161f0adae68692c67174771232c80675
Dependencies: #16439 | Stopgaps:
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Comment (by kcrisman):
> As you can see, it never quite makes it down to the horizontal axis.
If you use the endpoints 1 and 2, it does; 0 and 2 doesn't. (And
presumably didn't in the past, either.) Anyway, that is annoying, though
I'm not sure there is much to do about it.
Here is what is going on. For user-provided exclusion, we have
{{{
if isinstance(exclude, (list, tuple)):
exclude = sorted(exclude)
# We make sure that points plot points close to the excluded
points are computed
}}}
but we don't have something similar to that for the 'auto-excluded
points'. I don't see an easy way to do this, though.
I am also annoyed (this has nothing to do with this patch) by the
inconsistency between `exclude is not None`, `not exclude`, `exclude !=
None`, and so forth. There are subtle things that can happen here, though
I think that in this case they don't.
----
Now for something that I still see as a bug, though probably not a problem
for this ticket.
{{{
sage: polar_plot(sin(sqrt(x^2-1)), (x, 0, 2*pi), exclude=[2,3])
sage: polar_plot(sin(sqrt(x^2-1)), (x, 0, 2*pi), exclude=[1/2,2,3])
}}}
Compare these. The first one does just what you want. The second one
does not - presumably because I'm excluding a point already not in the
domain, but why does that cause a problem? The others should still be
there. You could say it's user error, but then again
{{{
sage: plot(x,(x,0,1),exclude=[-1,1/2])
}}}
works as desired, so I don't think that is why, and it occurs with and
without this change.
Actually, presumably this is via parametric from polar.
{{{
sage: parametric_plot((sqrt(x^2-1),sqrt(x^2-1/2)),(x,0,5), exclude=[2,3])
sage: parametric_plot((sqrt(x^2-1),sqrt(x^2-1/2)),(x,0,5),
exclude=[1,2,3])
}}}
Is this a new ticket, or a wontfix? I'm inclined to say this is a bug.
--
Ticket URL: <http://trac.sagemath.org/ticket/13246#comment:52>
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