[R] Matrix manipulation - dropping rows based on a query

James MacDonald
Tue, 22 Jul 2003 18:15:24 -0000

tst <- apply(my.mat, 2, mean) < 1

my.mat[,tst]

Will return only columns with mean < 1

Jim



James W. MacDonald
Affymetrix and cDNA Microarray Core
University of Michigan Cancer Center
1500 E. Medical Center Drive
7410 CCGC
Ann Arbor MI 48109
734-647-5623

>>> <monkeychump at hushmail.com> 07/22/03 01:53PM >>>

I have a matrix with some very funky data. I want to drop the columns
with a mean > 1 (for instance).
#Example:
my.mat <- matrix(rnorm(100, 0, 3), nrow = 10)

#I know I can get the row means:
apply(my.mat,1, mean)

I think I need to get a vector that has those rows > 1

my.mat[-rows>1,]

The actual querry is much more complicated but this gives an
approximation.

Thanks.









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