Re: [R] Extracting from a matrix w/o for-loop

From: Adrian DUSA <adi_at_roda.ro>
Date: Sat 29 Jul 2006 - 20:50:01 EST

Hi,

On Friday 28 July 2006 20:21, Horace Tso wrote:
> Unless there is another level of complexity that i didn't see here,
> wouldn't it be a simply application of sapply as follow,
>
> sapply( 1:dim(M2)[[1]], function(x) M1[M2[x,1], M2[x,2]] )

Andy's previous answer involving matrix indexing (M1[M2]) is simpler but just for the sake of it, since we're dealing with matrices it is not a case of sapply but of _apply_:

apply(M2, 1, function(x) M1[x[1], x[2]])

My 2c,
Adrian

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Adrian DUSA
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Received on Sat Jul 29 20:52:52 2006

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