How can I perform interpolation on points that lie within a radius certain using GRIDDATA in MATLAB (R2013a)?

I am working with datasets which have many millions of points and there is significant time involved in creating gridded data points.

I would like to perform interpolation only on points that fall inside a radius 'R' from a target point (X0,Y0). How can I do that? And is there a way I can retrieve the pairwise distances and obviate the need to recalculate them?

Answer 1

[MathWorks Support Team]

Unfortunately, one cannot retrieve the pairwise distances that are computed during the intermediate steps of the interpolation. However, to perform interpolation on scattered points that fall within a radius "R", you can follow these steps:

1. Say, I create some random data points (X,Y) and define their distance to the target point (X0,Y0)

>> X = rand(10,1);
>> Y = rand(10,1);
>> dX = X - X0;
>> dY = Y - Y0;
>> dists = sqrt(dX.^2+dY.^2);

2. We now find which points fall within a radius "R" from (X0,Y0) using logical indexing:

>> indices = d(d>R);
>> XqNew = Xq(indices);
>> YqNew = Yq(indices);

More on logical indexing:

https://www.mathworks.com/help/matlab/math/array-indexing.html