[Octave-bug-tracker] [bug #35178] griddata: cubic interpolation not yet implemented

[Rik]

Follow-up Comment #8, bug #35178 (project octave):

Matlab's description of "natural" and "cubic" isn't much help.  You might also
take a look at the documentation for interp1.  In that case, "cubic" is the
same as "pchip", which uses Hermite polynomials rather than just ordinary
cubic polynomials.

As a guess, it may be that the Delaunay triangulation is used to quickly
locate the 4 nearest points in the original source data to the query point and
then construct a cubic spline.  This could still be a win computationally,
when compared to interp2 (..., "spline"), because splines would only be
created for regions with query points.  In the case of interp2, it creates a
spline for every single gap between data points.

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