MATLAB: Cell array of coordinates from two vectors

cell arraycoordinatesvectors

I have two vectors, one with 119 X values and a one with 102 Y values. I'm trying to work out a way to combine these to create to all possible unique sets of coordinates (12,138 unique coordinates). I could use two nested for loops to do it, but it's very slow. I'm struggling to find if theres any combination of matlab functions that could achieve this.

Best Answer

No loops required, just use ndgrid and indexing:
>> X = randi(999,119,1); % must be column vector

>> Y = randi(999,102,1); % must be column vector
>> [idx,idy] = ndgrid(1:numel(X),1:numel(Y));
>> M = [X(idx(:)),Y(idy(:))];
>> size(M)
ans =
   12138       2
Here is a simpler example:
>> X = (1:5).';
>> Y = (6:9).';
>> [idx,idy] = ndgrid(1:numel(X),1:numel(Y));
>> M = [X(idx(:)),Y(idy(:))];
>> M
M =
   1   6
   2   6
   3   6
   4   6
   5   6
   1   7
   2   7
   3   7
   4   7
   5   7
   1   8
   2   8
   3   8
   4   8
   5   8
   1   9
   2   9
   3   9
   4   9
   5   9
Related Question