MATLAB: Creating a data array from a matrix

create data arraysread a matrix

Hi,
I have matrix1 of 39 x 39. I need to create X and Y arrays by reading elements from rows and columns of matrix1 in a certain way.
 X        Y
(2,1)    (1,2)
(3,1)    (1,3)
(4,1)    (1,4)
..
(39,1)   (1,39)
(3,2)    (2,3)
(4,2)    (2,4)
..
(39,2)   (2,39)
(4,3)    (3,4)
..
(39,3)   (3,39)
..
(39,38)  (38,39)
How can I implement in MATLAB? Can somebody help me.
Thanks in advance,

Best Answer

Hi Damith - I'd go with a double for loop, pre-allocating memory for the X and Y vectors:
 [m,n] = size(matrix1); % where matrix1 is the 39x39 matrix
 numElems = (m-1)*m/2;  % since ignoring elements on matrix diagonal
 X = zeros(numElems,1);
 Y = X;
 at = 1;
 for i=1:m
   for j=i+1:m          % since not interested in i==j
     X(at) = matrix1(j,i);
     Y(at) = matrix1(i,j);
     at = at + 1;
   end
 end
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