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

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

[Andrei Bobrov]

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

a(rs,:) = bsxfun(@plus,a(rs,:),b);

[Sujan]

was helpful. thank you

Answer 2

[Image Analyst]

Try this demo:

% Define sample data.
a = randi(9, 10, 4)
b = 100*ones(1, 4)

% Define the rows to add b to:
rowsToAddTo = [2 5 7 9]
% Do the addition:
a(rowsToAddTo, :) = a(rowsToAddTo, :) + repmat(b, [length(rowsToAddTo), 1])

In the command window

a =
   2     9     7     8
   6     5     8     7
   5     4     9     8
   8     6     5     3
   1     4     4     7
   6     3     8     8
   3     2     8     3
   6     4     5     5
   2     5     1     6
   4     9     3     6
b =
 100   100   100   100
rowsToAddTo =
   2     5     7     9
a =
   2     9     7     8
 106   105   108   107
   5     4     9     8
   8     6     5     3
 101   104   104   107
   6     3     8     8
 103   102   108   103
   6     4     5     5
 102   105   101   106
   4     9     3     6

[Sujan]

was helpful. thank you.