[R] How sum all possible combinations of rows, given 4 matrices

Jeff Newmiller jdnewmil at dcn.davis.CA.us
Mon May 27 18:40:31 CEST 2013

I expect the answer to involve manipulating indices. But why do you need to do this? This looks suspiciously like homework, and there is a no-homework policy on this list (see the Posting Guide).
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Sent from my phone. Please excuse my brevity.

"Estigarribia, Bruno" <estigarr at email.unc.edu> wrote:

>Hello all,
>I have 4 matrices with 3 columns each (different number of rows
>though). I
>want to find a function that returns all possible 3-place vectors
>corresponding to the sum by columns of picking one row from matrix 1,
>from matrix 2, one from matrix 3, and one from matrix 4. So basically,
>possible ways of picking one row from each matrix and then sum their
>columns to obtain a 3-place vector.
>Is there a way to use expand.grid and reduce to obtain this result? Or
>I on the wrong track?
>Thank you,
>PS:I believe I have given all relevant info. I apologize in advance if
>question is ill-posed or ambiguous.
>R-help at r-project.org mailing list
>PLEASE do read the posting guide
>and provide commented, minimal, self-contained, reproducible code.

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