[R] random section of samples based on group membership

From: Wade Wall <wade.wall_at_gmail.com>
Date: Tue 25 Jul 2006 - 01:18:10 EST


Hi all,

I have a matrix of 474 rows (samples) with 565 columns (variables). each of the 474 samples belong to one of 120 groups, with the groupings as a column in the above matrix. For example, the group column would be:

1
1
1
2
2
2
.
.
.

120
120

I want to randomly select one from each group. Not all the groups have the same number of samples, some have 4, some 3 etc. Is there a function to do this, or would I need to write a looping statement to look at each successive group?

I basically want to combine the randomly selected samples from the 120 groups into a new matrix in order to perform a cluster analysis.

Thanks,
Wade



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