#13167: Clarify some comments concerning the matplotlib Delaunay code in
list_plot3d.py
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Reporter: jdemeyer | Owner: mvngu
Type: enhancement | Status: positive_review
Priority: minor | Milestone: sage-5.2
Component: documentation | Resolution:
Keywords: | Work issues:
Report Upstream: N/A | Reviewers: Karl-Dieter Crisman
Authors: Jeroen Demeyer | Merged in:
Dependencies: | Stopgaps:
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Comment (by ppurka):
Replying to [comment:2 kcrisman]:
> Looks fine on the face of it. Applies fine, tests fine, code is the
same after all.
>
> Is it really the mpl code, then, not scipy? Hang on, I just haven't
looked at the whole file yet...
Yes. It is mpl code that is the problem here. Quoting from
[http://matplotlib.sourceforge.net/api/mlab_api.html#matplotlib.mlab.griddata
mpl docs],
{{{
If interp keyword is set to ‘nn‘ (default), uses natural neighbor
interpolation based on Delaunay triangulation. By default, this algorithm
is provided by the matplotlib.delaunay package, written by Robert Kern.
The triangulation algorithm in this package is known to fail on some
nearly pathological cases. For this reason, a separate toolkit
(mpl_tookits.natgrid) has been created that provides a more robust
algorithm fof triangulation and interpolation. This toolkit is based on
the NCAR natgrid library, which contains code that is not redistributable
under a BSD-compatible license. When installed, this function will use the
mpl_toolkits.natgrid algorithm, otherwise it will use the built-in
matplotlib.delaunay package.
}}}
So, essentially the delaunay code is not considered very robust.
Now, I had a look at the `natgrid` code and there is one file's license
which is the main problem I think, and due to which I believe it won't be
possible to distribute/include it in Sage.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/13167#comment:4>
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