Gap fill using two vectors without a loop

Question

Donald 2012-2-13

Suppose I have a binary vector x and I want to fill gaps longer than a certain threshold. Is there a way to do this without a loop?

Example: x = [1 0 0 0 1 1 1 0 0 1 1 0 1]; th = 1;

I can get a,b which are vectors that represent the start and stop indices of the gaps. a = [2 8 12]; b = [4 9 12];

Right now I'm doing:

y=x;
excNdx = find( b-a > th );
for iNdx = excNdx
    y(a(iNdx):b(iNdx)) = 1;
end

y = [1 1 1 1 1 1 1 1 1 1 1 0 1]

Also, any ideas for doing this down rows or columns of a matrix would be helpful also.

Answer 1

Sean de Wolski 2012-2-13

One of many ways:

x = [1 0 0 0 1 1 1 0 0 1 1 0 1]; 
th = 1; %greater than this
idx = strfind(x,zeros(1,th+1));
if ~isempty(idx)
  x(bsxfun(@plus,idx,(0:th)')) = 1
end