MATLAB: Find where number changes in a matrix

diff()find

I have a matrix of +1 and -1 values. I want to find where the number flips from 1 to -1 or vice versa where the change is a change from column to column.
X=[...
1  1  1  1;
1      -1  1  1;
1  1  1      -1;
1  1  1  1]
the answer should be [2,2],[2,3]and [3,4]. I tried
find(diff(X)==2);
find(diff(X)==-2);
Any help is appreciated

Best Answer

 >> [r,c] = find(diff(X,1,2)) ;
 >> loc = [r, c+1]
 loc =
     2     2
     2     3
     3     4
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