MATLAB: How to add arrays to specific rows of a matrix in single step

Question

Suppose I have a matrix A of size (k x n).

I want to add an array of size (1 x n) to some of the rows of this matrix, say rows (2,5,7,9).

How can this be done in single step ?

Answer 1

a = randi(9, 10, 4);
b = 100*ones(1, 4);
rs = [2 5 7 9];
a(rs,:) = bsxfun(@plus,a(rs,:),b);