#12277: Warnings in `plot_slope_field`
------------------------+---------------------------------------------------
Reporter: novoselt | Owner: jason, was
Type: defect | Status: needs_review
Priority: major | Milestone: sage-duplicate/invalid/wontfix
Component: graphics | Keywords:
Work_issues: | Upstream: N/A
Reviewer: | Author:
Merged: | Dependencies:
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Changes (by novoselt):
* status: new => needs_review
* milestone: sage-5.0 => sage-duplicate/invalid/wontfix
Old description:
> If I do (in Sage 4.7.2 or 4.8.alpha6)
> {{{
> plot_slope_field(1, (1,2), (3,4))
> }}}
> (or anything else that I have tried), then in front of the plot, which
> looks as expected, I get
> {{{
> Warning: divide by zero encountered in divide
> Warning: invalid value encountered in multiply
> Warning: invalid value encountered in multiply
> Warning: divide by zero encountered in divide
> Warning: invalid value encountered in multiply
> Warning: invalid value encountered in multiply
> }}}
>
> My investigation so far shows: this function is a little wrapper for
> `plot_vector_field` which sets new defaults for three options. If
> `headlength` is set to 0, there are warnings.
>
> A possible workaround is to set it to something small: 0.001 seems to
> work on the screen. However, since with `headaxislength=0` and
> `headlength=0.2` I definitely see "a hair on the end", it does not seem
> to be satisfactory from a perfectionist point of view (and producing
> vector formats that may be scaled or printed with high resolution).
>
> Besides, current settings do produce the accurate plot, it just shows
> warnings that should not be there, and I have no idea how to fix it.
New description:
Duplicate of #11208
If I do (in Sage 4.7.2 or 4.8.alpha6)
{{{
plot_slope_field(1, (1,2), (3,4))
}}}
(or anything else that I have tried), then in front of the plot, which
looks as expected, I get
{{{
Warning: divide by zero encountered in divide
Warning: invalid value encountered in multiply
Warning: invalid value encountered in multiply
Warning: divide by zero encountered in divide
Warning: invalid value encountered in multiply
Warning: invalid value encountered in multiply
}}}
My investigation so far shows: this function is a little wrapper for
`plot_vector_field` which sets new defaults for three options. If
`headlength` is set to 0, there are warnings.
A possible workaround is to set it to something small: 0.001 seems to work
on the screen. However, since with `headaxislength=0` and `headlength=0.2`
I definitely see "a hair on the end", it does not seem to be satisfactory
from a perfectionist point of view (and producing vector formats that may
be scaled or printed with high resolution).
Besides, current settings do produce the accurate plot, it just shows
warnings that should not be there, and I have no idea how to fix it.
--
Comment:
Yes, strange I couldn't find it, I tried to search... My current
workaround is that I have redefined `plot_slope_field`. It is in a way
good, since I also had to fix aspect ratio (for 4.7.2) and changed
defaults for colour and frame to match the textbook I am using.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/12277#comment:5>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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