# Re: [R] product of successive rows

From: Jorge Ivan Velez <jorgeivanvelez_at_gmail.com>
Date: Tue, 29 Jul 2008 07:13:47 -0400

Hi rcoder,

Assuming that the number of rows of your matrix x is even, try also:

x <- matrix(1:72,12)
apply(x,2, tapply, rep(1:(nrow(x)/2),each=2),prod)

# or using a function which argument "x" is your matrix

prod.mat=function(x) {
k=nrow(x)
g=rep(1:(k/2),each=2)
apply(x,2, tapply, g,prod)
}

prod.mat(x)

HTH, Jorge

On Sun, Jul 27, 2008 at 6:20 PM, rcoder <mpdotbook_at_gmail.com> wrote:

>
> Hi everyone,
>
> I want to perform an operation on a matrx that outputs the product of
> successive pairs of rows. For example: calculating the product between rows
> 1 & 2; 3 & 4; 5 & 6...etc.
>
> Does anyone know of any readily available functions that can do this?
>
> Thanks,
>
> rcoder
>
>
> --
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>
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