[SciPy-Dev] Splines

denis denis-bz-py@t-online...
Wed Mar 13 13:54:03 CDT 2013


Charles R Harris <charlesr.harris <at> gmail.com> writes:

> I'm not sure you are interpreting 'prefilter' correctly. I haven't looked at
the scipy code, but the uniform spline coefficients can be gotten by filtering
forward and back along each axis. It essentially factors the fit matrix into
lower/upper factors with constant diagonals modulo boundary conditions, and
forward/reverse substitution reduces to IIR filtering. This is also used for
other interpolation schemes, for instance variance preserving interpolation
which is useful when matching scenes using mutual information.Chuck

Chuck,
  is "prefilter=True will filter out high frequencies in the data"
not correct ?  It's a pure preprocessing step,
spline_filter in ndimage/interpolation.py
iterates spline_filter1d Bspline smoothing along each axis.

How about running some testfunctions with / without prefilter,
do you know of any real or realistic ?

cheers
  -- denis



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