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

[Peter G. <pgr...@ge...>]

Perry Greenfield wrote:

>
> 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.


I use Hardy's multiquadric interpolation to to do the math,  then use 
imshow (or pcolor) to make a surface map.  I only have data for the 120 
points (where the circle are - those are actuators), and interpolate the 
rest.

If people are interested, I can clean up the code a little and post it.