MATLAB: Conditional cumsum – how to create

Question

This is probably easy, but my brain isn't working today…

How can you do the following operation in a vectorized way? I'd think it should be possible with some combination of cumsum, diff & logical indexing:

input = rand(10,1);
output = zeros(size(input);
output(1) = input(1);
for ind = 2:numel(input)
  dif = input(ind) - input(ind-1);
   if dif < 0
      output(ind) = output(ind-1) + dif;
   else
      output(ind) = output(ind-1);
   end
end

Answer 1

Try this.

 outp = cumsum([inp(1);min(diff(inp),0)]);