MATLAB: Closest coordinate points between two data sets

coordinatedsearchnintersectnearestpdist2Statistics and Machine Learning Toolbox

I have two data sets of different sizes, one of which is a 15×3 matrix of latitude, longitude, and concentration data and the other of which is a 2550×3 matrix, also composed of latitude, longitude, and concentration data. I want to find the coordinates in the first data set that are closest to those in the second, larger set. Then based on the index locations of those coordinates in the larger matrix, extract out the concentration values from that correspond to those coordinates so that I can plot the two sets of concentrations against one another. The difficult part of this is that the coordinate locations in the smaller matrix do not align perfectly with those in the larger matrix, so I would like to be able to find the closest possible coordinate locations between the two matrices.
For example:
Matrix 1
A = [
 -62.232  47.993  6.3
 -63.321  49.888  5.4
 -63.442  50.201  2.1
 -63.845  51.268  9.7]
Matrix 2
   B = [
   -62.859  48.918  4.9
   -63.987  49.971  3.0
   -62.234  47.990  4.6
   -62.909  48.236  5.7
   -63.325  49.885  7.1
   -64.897  48.032  6.3
   -63.440  50.200  5.9
   -62.921  51.679  3.2
   -63.849  51.270  4.5
   -64.018  50.327  2.6]
The intersect function does not produce any intersection points because of the mismatch in the coordinates, so I have attempted to use the pdist2 function and dsearchn, but to no avail.
I would like to produce a matrix of indices of the matrix B where the longitude and latitude values are closest to those in matrix A.
For example:
Result (from Matrix B)=
   -62.234  47.990  4.6
   -63.325  49.885  7.1
   -63.440  50.200  5.9
   -63.849  51.270  4.5
Indices=
   3   3   3
   5   5   5
   7   7   7
   9   9   9
With the end goal being B(indices), allowing me to plot B(:,3) against A(:,3).
Please let me know if you need any more information regarding my issue- thank you!

Best Answer

One way to do it would be to use interp2() in which your X and Y values were your lat and long, and your Z value is corresponding matrix linear indices (integers), and you set the interpolation method to 'nearest'. Then interpolate the other coordinates in order to get out the indices into the first matrix.
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