interpn vs griddata: how are results different?

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Starting off from here:
A=data;
[X,Y,Z]=ndgrid(1:61,1:73,1:61);
x2=linspace(1, 61, 31);
y2=linspace(1, 73, 37);
z2=linspace(1, 61, 31);
[X2 Y2 Z2]=ndgrid(x2, y2, z2);
How are these variables below different? The correlation between data1 and data2 is r=.97.
data1=interpn(X2,Y2,Z2, A, X, Y, Z, 'linear');
data2=griddata(X2,Y2,Z2,A,X,Y,Z,'linear');
Thank you!

Answers (1)

Bruno Luong
Bruno Luong on 10 Aug 2020
Mathematical, in short the difference is
  • INTERPN uses tensorial linear function on nd-hypercube that enclose the query point.
  • GRIDDATA uses linear function on nd-simplex the query point
  3 Comments
Bruno Luong
Bruno Luong on 11 Aug 2020
Edited: Bruno Luong on 11 Aug 2020
INTERPN is faster and provides interpolation result more smooth (C1-discontinuouson smaller set) and better symmetric (invariant if you exchange coordinates) than GRIDDATA. If you have initial point on grid use INTERPN.
Use GRIDDATA only when you can't use the other (scattered data).

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