Re: [unclassified] contourc

[Kai Habel]

Alexander Barth schrieb:
> Hi all,
> I seems that there are several implementations for computing contours: 
> the __contourc__.cc originally from plplot and the script 
> implementation in contourf.m from octplot. For me, the implementation 
> in contourf.m works more reliably than the __contourc__.cc 
> implementation. __contourc__.cc produces sometimes discontinuous 
> contour lines. As contourf.m is written, it would be very easy to 
> extract the contour generation code and make a new contourc.m to 
> replace __contourc__.cc.
>
> I would also be interested to implement arbitrary quadrilateral meshes.
> What do you think?
>
> Thanks,
> Alex
Hello Alexander, Hello all,

as far as i know there are two implementations for computing contours. 
The 'old' __contourc__.cc (before April 07) from octplot (originating 
from plplot etc.) and a improved 'new' version (April' 07) also from 
octplot to support filled contours. This was required (as you have 
noticed), because the 'old' version generates in some cases broken contours.
The 'old' version has also been included in the octave tree.

If you talk about the octplot/contourf.m implemetation, this does not 
include any contour finding as it relies on contourc.m/__contourc__.cc 
for this purpose. The combination of contourf.m and __contourc__.cc from 
octplot should work pretty well.

Unfortunately the 'new' version of __contourc__.cc (also to be found in 
the octplot svn) has some problems as well. So, I have a third version 
of __contourc__.cc - a major rewrite, which is almost finished. I plan 
to post it for discussion on the maintainers list very soon. (If all 
works out well, maybe this week).

Regarding your last question, is this related to this thread [1] or a 
more general approach?

Kai

[1] 
http://www.nabble.com/contour-plots-only-work-for-meshgrid-%28uniform%29-spaces-and-not-other-spaces.-tf4541422.html