Hi, I am trying to use griddata to interpolate some irregularly spaced data
onto a linspace-created mesh in order to get a temperature plot.
I've been able to follow this example and it's worked perfectly for me:
http://matplotlib.sourceforge.net/examples/pylab_examples/griddata_demo.html
However, when I do my own data I get an error message that says:
>
> Traceback (most recent call last):
> File "make_colormap.py", line 248, in <module>
> zi=griddata(x,y,z,xi,yi,interp='linear')
> File "/usr/lib/pymodules/python2.6/matplotlib/mlab.py", line 2579, in
> griddata
> raise ValueError("output grid must have constant spacing"
> ValueError: output grid must have constant spacing when using
> interp='linear'
Looking into the documentation it seems that this is just suggesting that
the xi,yi grids to be interpolated on have constant spacing. I don't know
if this is supposed to be the SAME constant spacing in xi and yi, but it
appears not to be, since the example above uses the line:
xi = np.linspace(-2.1,2.1,100)
> yi = np.linspace(-2.1,2.1,200)
so one is twice as fine as the other.
However, my code, when I do something like
> xi=linspace(-20.1,20.1,100)
> yi=linspace(-20.1,20.1,200)
> zi=griddata(x,y,z,xi,yi,interp='linear')
> CS=plt.contourf(xi,yi,zi,15,cmap=plt.cm.jet)
it gives me the above error complaining about "constant spacing".
Anyone have an idea what I might be missing here? I can turn interp to 'nn'
and the code works fine, but I'm just curious what about a "constant
spaced" output grid I don't understand. Is it even possible to create a
non-constant spaced output grid with linspace?
Thanks for the help!
Brad
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