# How to count the number of 1 between two 0 in a vector?

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Nicolò Castellani on 3 Feb 2020
Commented: Adam Danz on 4 Feb 2020
I have this vector:
[0 1 1 1 0 0 1 0 1 1 0 1]
I want to create a vector that every time that I have 1 or more consecutive 1 it counts the number of 1 between two zero. So the results must be:
[3 1 2 1]
How can I do that?
thanks

Adam Danz on 3 Feb 2020
Edited: Adam Danz on 3 Feb 2020
In both methods below,
A is the input vector (row or column)
B is the output vector of consecutive 1 counts, row vector.
Method 1 assumes the vector only contains 1s and 0s
A = [0 1 1 1 0 0 1 0 1 1 0 1];
B = diff(find([0,A(:).',0]==0))-1;
B(B==0) = [];
Method 2 counts consecutive 1s, other elements can take any numeric value.
A = [0 1 1 1 0 0 1 0 1 1 0 1];
dA = diff([0,A(:).',0]==1);
B = find(dA==-1)-find(dA==1)

Sean de Wolski on 3 Feb 2020
[regionprops(bwlabel([0 1 1 1 0 0 1 0 1 1 0 1]),'Area').Area]

Adam Danz on 3 Feb 2020
I was also thinking about using bwlabel for those who have the Image Processing Toolbox.
A = [0 1 1 1 0 0 1 0 1 1 0 1];
B = histcounts(bwlabel([0,A(:).',0]),'BinMethod','integer');
B(1) = [];
Sean de Wolski on 4 Feb 2020
A vector is just a long and skinny image! I find things like bwlabel, bwareaopen, etc. to often be useful for this kind of thing.
Adam Danz on 4 Feb 2020
Agreed - I'm relatively new to the bw.... functions but I use bwlabel often. Since it requires access to a toolbox I went with a lower level solution in my answer.