Question

For example:

a=[1 1 0 0 1 1 0 1 1 1 0 0];

Now i want to sum only the ones which are divides by the zeros:

ones=[2 2 3] – That means two ones,then we have 2 zeros which we do not count,then again two ones etc.

How can i do this?

Answer 1

Well, I would suggest finding all places where it switches from 0 to 1 and then finding all places where it switches from 1 to 0, and using those indices to find those lengths. The problem arises at the edges where if the first entry is 1, it doesn’t switch to one from zero, and if the last entry is 1, we never find it because nothing switches to 0 at the end. In order to avoid this problem easily, we can add a 0 in the beginning and one at the end. This way we’re guaranteed to find each one of those bursts of ones. In essence:

b = [0 a 0];
d = diff(b);

posEdge = find(d==1);
negEdge = find(d==-1);

countOnes = negEdge - posEdge