How to add arrays to specific rows of a matrix in single step ?
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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 ?
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Accepted Answer
Andrei Bobrov
on 16 Jan 2013
a = randi(9, 10, 4);
b = 100*ones(1, 4);
rs = [2 5 7 9];
a(rs,:) = bsxfun(@plus,a(rs,:),b);
More Answers (1)
Image Analyst
on 16 Jan 2013
Edited: Image Analyst
on 16 Jan 2013
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
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