# [R] splitting matrices

arun smartpink111 at yahoo.com
Thu Jan 3 18:12:11 CET 2013

```Hi,
You could also try:
set.seed(51)
mat1<-matrix(sample(1:5000,1116*12,replace=TRUE),nrow=1116)
dim(mat1)
#[1] 1116   12

res1<-lapply(split(as.data.frame(mat1),rep(1:36,each=31)),as.matrix)
unlist(lapply(res1,nrow))
# 1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26
#31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31
#27 28 29 30 31 32 33 34 35 36
#31 31 31 31 31 31 31 31 31 31

A.K.

----- Original Message -----
From: "MacQueen, Don" <macqueen1 at llnl.gov>
To: eliza botto <eliza_botto at hotmail.com>; "r-help at r-project.org" <r-help at r-project.org>
Cc:
Sent: Thursday, January 3, 2013 11:56 AM
Subject: Re: [R] splitting matrices

This example illustrates a method that may do what you want.

## split a 20x5 matrix into five 4x5 matrices
xmat <- matrix(1:100, nrow=20, ncol=5, byrow=TRUE)
xsplit <- rep( 1:5, times= rep(4,5))
tmp <- split.data.frame(xmat,xsplit)

You will need to change xsplit to fit your dimensions.

-Don

--
Don MacQueen

Lawrence Livermore National Laboratory
7000 East Ave., L-627
Livermore, CA 94550
925-423-1062

On 1/3/13 8:40 AM, "eliza botto" <eliza_botto at hotmail.com> wrote:

>
>
>Dear useRs,
>i want to split a matrix having 1116rows and 12 columns. i want to split
>that matrix into 36 small matrices each having 12 columns and 31 rows.
>The big matrix should be splitted row wise. which means that the first
>small matrix should copy values which are in first 31 rows and 12 columns
>of the big matrix. similarly 2nd small matrix should contain values from
>32nd to 63rd row of the big matrix and so on. on the whole i want to have
>36 small matrices.i tried
>dim(dd) <- c(31,12,35)
>but the result are not stisfactory...
>elisa
>    [[alternative HTML version deleted]]
>
>______________________________________________
>R-help at r-project.org mailing list
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>and provide commented, minimal, self-contained, reproducible code.

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