select randomly "N" rows of a matrix?

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Noe alvarado
Noe alvarado 2012-4-12
how i can select randomly "N" rows of a matrix? for example
M =
[ a12, a12]
[ a21, a22]
[ a31, a32]
[ a41, a42]
For N=2
B =
[ a12, a12]
[ a31, a32]
[ a21, a22]

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Thomas
Thomas 2012-4-12
try:
N=2; % no. of rows needed
M=rand(5) % generate a 5x5 matrix random
c=randperm(length(M),N)
B=M(c,:) % output matrix
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Jan
Jan 2012-4-12
@Noe, Then use: c = randperm(size(M, 1)); c = c(1:N);

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