MATLAB: TriScatteredInterp not interpolating as expected

scatteredinterpolanttriscatteredinterp

I tried to interpolate a set of radar reflectivity values using TriScatteredInterp (and later with scatteredInterpolant). As my initial data had quite a few NaN values, the final interpolation incorrectly created an entire array of NaNs. I tried repeating the interpolation by subbing "-50" in for the NaNs (I can erase bad data after), but when I do that, TriScatterdInterp still returns an antire array of NaNs, and scatteredInterpolant fills the entire array with -50, which is also incorrect. The data and code has been attached. Any ideas what may be wrong?
(I tested it out on a small sample of test data and it worked, but still returns all NaNs or all -50 when I apply it to my dataset).
"initial_heights.m" = z_radar_dn in code. "original_dbz.m" = dbz_dn_sub_thresh in code.
% Prep input arrays
heights = z_radar_dn(:,:)';
x = 1:4443;
x = repmat(x,413,1);
dbz_initial = dbz_dn_sub_thresh(:,:)';
dbz = dbz_initial;
% Replace NaN's with -50 for interpolation
replace = isnan(dbz);
dbz(replace) = -50;
% Flatten to vectors
%F_ref = scatteredInterpolant(double(x(:)),double(heights(:)),double(dbz(:)));
F_ref = TriScatteredInterp(double(x(:)),double(heights(:)),double(dbz(:)));
% Set up a perfect grid
xvec = [1:4443];
maxHeight = max(z_radar_dn(1,:))*1000;
n = floor(maxHeight/30);
zvec = [maxHeight:-30:maxHeight-(n*30)];
% Mesh them together
[xmat,zmat]=meshgrid(xvec,zvec);
% Interpolate
dbz_interpolated= F_ref(xmat(:),double(zmat(:)));
% Reshape
dbz_interpolated=reshape(dbz_interpolated, size(xmat));

Best Answer

When you create the interpolant the second variable corresponding to y is your height variable. When you go to use the interpolant you are passing z as the second variable. Most of your z are not in the same range as your height so the interpolant is applying its default extrapolation of putting in nan.
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