MATLAB: Finding the number of rows to the next row containing a 1

Question

Hi

I have a column vector of 1s and 0s and I want to find find the number of rows to the next row containing a 1. For example:

A = [0 0 0 1 0 1 1 1 0 0 0 0 0 1]';

I would like the code to return

B = [3 2 1 0 1 0 0 0 5 4 3 2 1 0]';

Is there a vectorized way that this can be done?

Thanks in advance

Answer 1

It took some time, but here is a solution that should also work for large matrices.

clc,clear
format compact
A = [0 0 0 1 0 1 1 1 0 0 0 0 0 1]';
%    3 2 1 0 1 0 0 0 5 4 3 2 1 0
B=A;
pad=B(end)~=1;
if pad,B(end+1)=1;end %this method requires the last position to be a 1
B=flipud(B);
C=zeros(size(B));
C(B==1)=[0;diff(find(B))];
C=ones(size(B))-C;
out=cumsum(C)-1;
out=flipud(out);
if pad,out(end)=[];end
%only for display:
[A out]