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

[Uwe Ligges]

James MacDonald wrote:
> tst <- apply(my.mat, 2, mean) < 1

... and
  rowMeans(my.mat) < 1
will be faster, but perhaps not working for the requested "more 
complicated query".

Uwe Ligges

> 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.
>