title: 3D Extrapolation in python (basically, scipy.griddata extended to extrapolate)
body: <p>I am using the griddata function in scipy to interpolate 3 and 4 dimensional data. It works like a champ, except that it returns a bunch of NaNs because some of the points I need are outside the range of the input data. Given that N-d data only works with the "linear" mode interpolation anyway, it should be a snap to have griddata do an extrapolation instead of just returning NaN. Has anyone done this or found a workaround? To clarify: I have unstructured data, so I can't use any of the functions that require a regular grid. 
  Thanks!
  Alex</p>