# [R] sort (all columns of) a matrix

Daniel Malter daniel at umd.edu
Thu Oct 8 20:32:21 CEST 2009

```I assume you want to sort the whole dataset (matrix) by ordering one column
in ascending order (and order all other columns appropriately).

a<-matrix(a<-c(1,3,4,6,6,4,6,56,4,64,86,39,4,2),length(a),2)
a

#sort by first column
a[order(a[,1]),]

#sort by second column
a[order(a[,2]),]

#both give the same result here because the columns are identical

HTH,
Daniel

-------------------------
cuncta stricte discussurus
-------------------------

-----Ursprüngliche Nachricht-----
Von: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] Im
Auftrag von Kajan Saied
Gesendet: Thursday, October 08, 2009 12:51 PM
An: r-help at r-project.org
Betreff: [R] sort (all columns of) a matrix

Dear R-Help Team,

I have been trying to sort (all columns of) a matrix:

> a<-matrix(a<-c(1,3,4,6,6,4,6,56,4,64,86,39,4,2),length(a),2)
> a
[,1] [,2]
[1,]    1    1
[2,]    3    3
[3,]    4    4
[4,]    6    6
[5,]    6    6
[6,]    4    4
[7,]    6    6
[8,]   56   56
[9,]    4    4
[10,]   64   64
[11,]   86   86
[12,]   39   39
[13,]    4    4
[14,]    2    2
>
I would like to have the matrix sorted and the output should again be *a
matrix* with nrow=length(a) and ncol=2 just like (a) but only sorted.
Whatever I try (be it sort(), order()...) I receive a vector of
length(a)*2...

Best regards,

kajan

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