MATLAB: Finding a value and call the cell number or counting value on the same length of vectors.

Question

I'd like to call the row number when B(i,1)==1;

For i=1:n;
if B(i,1)==1;

(strfind is only for 1 row.) how to call the row and column number ?

or

for i=1:n;
if B(i,1)=1;    % when B(i,1)==1,  how to count 1 value and add 1

like

 1 0 0 0 1 0 0 1 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0 1
 1 0 0 0 2 0 0 3 0 0 0 0 4 0 0 0 0 0 0 5 0 0 0 0 0 6 0 0 0 0 7 ..

Thank you so much.

Answer 1

Using vectorized code is faster and neater than using a loop:

>> X = [1 0 0 0 1 0 0 1 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0 1];
>> Y = cumsum(X);
>> Y(X==0) = 0
Y =
  1   0   0   0   2   0   0   3   0   0   0   0   4   0   0   0   0   0   0   5   0   0   0   0   0   6   0   0   0   0   7