Re: Contour plots [Was: Re: [Matplotlib-users] how to make matplotlib faster?]

[Perry G. <pe...@st...>]

On Dec 9, 2004, at 2:12 PM, Chris Barker wrote:

> LUK ShunTim wrote:
>> As it's being implemented, here is a little wish. I'd like to see the 
>> capability of contouring on an arbitrary grid. That is, matplotlab 
>> would be able to plot the contours of a function f(x_i, y_i) given on 
>> an arbitrary set of points (x_i, y_i), not necessarily set out on a 
>> regular grid.
>
> This would be nice, but it's a bit of a project. One way to do it 
> would be to Delaunay triangulate the points, then you can compute the 
> contours from the triangular grid. Delaunay triangulation is not 
> trivial, and you really want to use an efficient scheme to do it. One 
> possibility is:
>
> http://www-2.cs.cmu.edu/~quake/triangle.html
>
> It is very robust and fast, and can be compiled as a library. I've 
> been planning for ages to write a Python wrapper for it, but haven't 
> gotten to it yet.
>
> If someone works on this, I'd like to help.
>
> -Chris
>

Actually, I believe that the low level contour engine we are using
supports this. It takes 2-d arrays for both x and y that represent
the x and y coordinates of the array being contoured and generates
plotting points based on those x and y arrays. These arrays allow
for irregular grids. At the moment, the routine generates uniform
x and y grids as arguments to pass along, but it could be generalized
to take these as extra arguments without much trouble.

Let me know if I misunderstand what you are trying to do.

Perry