MATLAB: Interpolation using scattered query points

griddedinterpolantinterpolationMATLABscattered query points

Hi
It is straight forward to use interpn or griddedInterpolant to perform n-dim interpolation. However, in these functions, the query points must be on a full grid. Is it possible to perform interpolation on a scattered set of query points?
As an example, for 2D interpolation, I don't want to perform interpolation on a full xy grid. I just want to perform interpolation on a set of points {(x1,y1), (x2,y2), (x3,y3), …}. I know it can be done using a loop, but I was looking for a faster and more efficient vectorized solution.
The question at the link below is similar to my question, but the answer didn't give a vectorized solution.
https://www.mathworks.com/matlabcentral/answers/336027-interpolation-in-an-image-at-specific-query-points
Thanks

Best Answer

I believe the solution you point to can be trivially vectorized:
load clown ;
imagesc(X);
colormap gray ;
[nx,ny] = size(X) ;
r = 1:ny ;
c = 1:nx ;
[R,C] = meshgrid(r,c) ;
%%do interpolation 
Ri = [5 6]; Ci = [5 7];    % <-------   I VECTORIZED THE CODE RIGHT HERE.
Xi1 = interp2(R,C,X,Ri,Ci) ;
% or can be used without mesh grid like below
Xi2 = interp2(r,c,X,Ri,Ci) ;
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