[Octave-bug-tracker] [bug #30587] buggy implementation of bicubic interpolation in interp2/bicubic

[Thorsten Meyer]

Follow-up Comment #2, bug #30587 (project octave):

Dear Marco,

thanks for your feedback.

1. You mention the case where xi and yi are vectors of the same length and
orientation. At the moment, interp2 passes these to bicubic.m and there they
will be used to define a meshgrid on which to interpolate. You say that the
two vectors should be interpreted as scattered vectors instead (giving only a
vector of interpolated values). If I understand you correctly, interp2 would:
 - interpret xi, yi as vectors of scattered data if xi and yi are of same
length and orientation
 - use xi, yi to define a meshgrid when they have different orientation
and/or different length

I personally would prefer an explicit option to force interp2 to treat xi, yi
vectors this or the other way. What does matlab do in these cases?

2. You ask, why I should give xi, yi as matrices, if they represent scattered
data. Well, actually, I was trying to understand the existing code and found
only this way to get the bicubic interpolation algorithm within interp2 to be
used. I also don't think, that such a use would be particularly useful (once
issue 1 above has been resolved in some way).

Regards

Thorsten

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