[R] ifelse, evaluating to given number

Adaikalavan Ramasamy ramasamy at cancer.org.uk
Mon Jul 19 01:23:45 CEST 2004


Is this what you want ?

> m <- matrix( 1:12, nc=3 )
> m
     [,1] [,2] [,3]
[1,]    1    5    9
[2,]    2    6   10
[3,]    3    7   11
[4,]    4    8   12

> ifelse( m < 6.5, 999, m )
     [,1] [,2] [,3]
[1,]  999  999    9
[2,]  999  999   10
[3,]  999    7   11
[4,]  999    8   12


On Mon, 2004-07-19 at 00:08, Peter Wilkinson wrote:
> I would like to take advantage of the  vectorized 'ifelse' command. Given a 
> filter number of 'filter', if the nm'th value in a n x m matrix I would 
> like to perform the following.
> 
> newMatrix <- ifelse(myMat <=filter, filter+1, "existing nm'th value").
> 
> What do I use to express the "existing nm'th value" in this expression if I 
> want to test an nm th value is less than 'filter', if false use the 
> existing nm'th value.
> 
> This does not seem to be documented in the help().
> 
> Peter W.
> 
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