Change a value in a matrix randomly

Tena koe Judit

If it is really a matrix (and not a data.frame) and you wish to change a randomly selected zero to a one, then

judit <- matrix(0, nrow=3, ncol=4)
judit[sample(1:length(judit), 1)] <- 1

will do.  This uses the fact that a matrix is a vector with a dim attribute.

HTH ....

Peter Alspach

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
project.org] On Behalf Of Barroso, Judit
Sent: Wednesday, 10 November 2010 10:50 a.m.
To: r-help at r-project.org
Subject: [R] Change a value in a matrix randomly

I have a matrix of ceros, for example:
0              0              0              0
0              0              0              0
0              0              0              0
And I would like that one of these values turn into 1, for example if
one condition is got, but not in a concrete position if not randomly.
Could you indicate me the code to can get it?

Thanks in advance,
Judit Barroso

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