# Replace 1's with 0's if there is less that five 1's between 0's in vector

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Eric on 1 Apr 2017
Answered: the cyclist on 1 Apr 2017
Hi everyone,
I want to replace 1's with 0's if there are less than five 1's between the zeros in a large vector. For example, I have the following vector:
x = [1; 1; 1; 1; 1; 1; 0; 1; 1; 1; 0; 1; 1; 1; 1; 1; 1; 0; 1; 1; 1; 1; 1; 1; 1; 0];
And I would like to create a script that can find and replace only the 1's where there are less than five 0's in between, which would end up with the following results with the example from above:
x = [1; 1; 1; 1; 1; 1; 0; 0; 0; 0; 0; 1; 1; 1; 1; 1; 1; 0; 1; 1; 1; 1; 1; 1; 1; 0];
Eric

the cyclist on 1 Apr 2017
Here is one way:
x = [1; 1; 1; 1; 1; 1; 0; 1; 1; 1; 0; 1; 1; 1; 1; 1; 1; 0; 1; 1; 1; 1; 1; 1; 1; 0];
[b n bi] = RunLength(x);
shortOneRunIndex = find(b'==1 & n<5);
for ns = shortOneRunIndex
x(bi(ns):bi(ns+1)-1) = 0;
end
This algorithm assumes that the sequence ends with a zero, as your example did. It could be fixed up to not require that assumption.