MATLAB: Counting consecutive occurences of 1s and -1s

count consecutivecounting 1s -1s

Hi, I have a vector containing -1,0 & 1. I want to count consecutive occurences of 1s & -1s.
If the input vector A = [0 0 1 1 1 1 0 0 0 -1 -1 -1 0 1 1 0 ], then I want an output which is Y = [4 -3 2]. (So the output vector is consecutive occurences of 1s and -1s with their sign).
Thanks

Best Answer

The first step below counts all consecutive numbers. The second step eliminates the 0-counts. 
A = [0 0 1 1 1 1 0 0 0 -1 -1 -1 0 1 1 0 ]; 
changeIdx = [1,diff(A)]~=0; 
counts = histcounts(cumsum(changeIdx),1:sum(changeIdx)+1); 
consecutiveCounts = [A(changeIdx)',counts']
% Result:
consecutiveCounts =
     0     2            %First there are 2 zeros
     1     4            %then 4 ones
     0     3            %then 3 zeros
    -1     3            %then 3 negative ones
     0     1            % etc...
     1     2
     0     1
To get the vector you described, eliminate the 0-counts and multiply by the sign of the value in A so counts of negative numbers are negative. 
  consecutiveCounts(consecutiveCounts(:,1)~=0,2)' .* sign(consecutiveCounts(consecutiveCounts(:,1)~=0,1))'
ans =
     4    -3     2
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