[SciPy-user] interpolation question

John Travers jtravs@gmail....
Wed Oct 17 14:17:09 CDT 2007


Hi Micheal,

On 17/10/2007, Michael Hearne <mhearne@usgs.gov> wrote:
>
> Is the 'linear' option in interpolate.interp2d() doing 'bilinear'
> interpolation, or something else?

Something else. It should be bilinear, but the underlying code is
designed for scattered grids of data and therefore has a more
complicated algorithm.

For regular girds (like yours) you should use RectBivariateSpline
------------------------------
from scipy.interpolate import RectBivariateSpline

# code in between

outgrid = RectBivariateSpline(xrange,yrange,data,kx=1,ky=1)
------------------------------

This gives me the same results as your matlab run.

Note that the input x and y are 1d arrays rather than 2d.
RectBivariateSpline is generally much more robust for regular grids,
and should be used unless you really do have scattered data.

Note to other developers: RectBivariateSpline should be used in
interp2d when possible. If I get time at the end of the month I'll do
this.

Cheers,
John


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