[R] matrix indexing

[Andy Bunn]

> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch
> [mailto:r-help-bounces at stat.math.ethz.ch]On Behalf Of tom wright
> Sent: Wednesday, March 15, 2006 6:04 AM
> To: R-Stat Help
> Subject: [R] matrix indexing
> 
> 
> Can someone please give me a pointer here.
> I have two matrices
> 
> matA
> 	A	B	C
> 1	5	2	4
> 2	2	4	3
> 3	1	2	4
> 
> matB
> 	A	B	C
> 1	TRUE	FALSE	TRUE
> 2	FALSE	TRUE	TRUE
> 3	FALSE	FALSE	FALSE
> 
> how do I extract all the values from matA where the coresponding entry
> in matB == TRUE (or FALSE), perferably in vector form.

Lie this?
matA <- matrix(c(5,2,1,2,4,2,4,3,4),3,3)
matB <- matrix(c(T,F,F,F,T,F,T,T,F),3,3)
matA[matB]
matA[!matB]


> 
> Many thanks
> tom
> 
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