MATLAB: Find the values before an element repeated more than 4 times.

repeated element

Hi everyone,
I have an array like this: A=[ 1 2 3 4 5 0 0 6 7 0 9 0 0 0 10 11 12 0 0 0 0 0 0 0 8 9 10 11 0 0 0 0 0 ]
I would like to find the values which are the ones before 0 repeated more than 4 times.
So here the answer should be 12 and 11.
Any help is appreciated.

Best Answer

Input: A, numeric row vector
Output: valueBefore, a numeric vector of values prior to 4 or more consecutive 0s. 
A=[ 1  2  3  4  5  0  0  6  7  0  9  0  0  0  10  11  12  0  0  0  0  0  0  0  8  9  10  11  0  0  0  0  0  ]; 
dA = diff([inf,A,inf]==0); 
zeroCount = find(dA==-1) - find(dA==1);
zeroStart = find(dA==1); 
valueBefore = A(zeroStart(zeroCount>=4)-1);
Note, if the A vector starts with 4+ zeros, there will be an error since there are no values prior to the first element.
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