MATLAB: Vectorized method to sum missed one values

performancevectorization

Hi there,
I am trying to achieve something, but I can't think of a vectorized way of doing this. The problem is as follows.
Say I have a vector of 0's and 1's, e.g. [0, 1, 1, 0, 0, 1, 0, 1]. Then I want to manipulate it in such a way that I get the following vector: [0, 2, 1, 0, 0, 3, 0, 2]. Hence, from left to right, every time a 1 occurs, it adds the number of consecutive preceding zero's, if any.
This can easily be done in a loop, but because of the vast number of computations, I am looking for a vectorized way to achieve this.
Any help is appreciated!
Best, Robert

Best Answer

A=[0, 1, 1, 0, 0, 1, 0, 1];
[~,NonZr] = find(A~=0);
A(NonZr) = [NonZr(1),NonZr(2:end)-NonZr(1:end-1)];
Result:
A =
     0     2     1     0     0     3     0     2
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