[R] product of successive rows

[jim holtman]

Does this do what you want:

> x <- matrix(1:36,6)
> x
     [,1] [,2] [,3] [,4] [,5] [,6]
[1,]    1    7   13   19   25   31
[2,]    2    8   14   20   26   32
[3,]    3    9   15   21   27   33
[4,]    4   10   16   22   28   34
[5,]    5   11   17   23   29   35
[6,]    6   12   18   24   30   36
> # create indices (going to assume an even number of rows
> x.ind <- seq(1, nrow(x), by=2)
> t(sapply(x.ind, function(.ind) x[.ind,] * x[.ind+1,]))
     [,1] [,2] [,3] [,4] [,5] [,6]
[1,]    2   56  182  380  650  992
[2,]   12   90  240  462  756 1122
[3,]   30  132  306  552  870 1260
>


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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> Sent from the R help mailing list archive at Nabble.com.
>
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-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem you are trying to solve?