[R] matrix indexing

[Gabor Grothendieck]

Try this:

matA[c(matB)]

In fact even this works for your example although in general it
couldbe problematic since a two column matrix index has
special meaning:

matA[matB]


On 3/15/06, tom wright <tom at maladmin.com> wrote:
> 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.
>
> Many thanks
> tom
>
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