Creating matrices

A matrix can be created by rows instead of by columns, which is done by using the byrow parameter, as follows:

m<-matrix(c(1,2,3,4,5,6), nrow=2, ncol=3,byrow=TRUE)
m
##      [,1] [,2] [,3]
## [1,]    1    2    3
## [2,]    4    5    6

With the dimnames parameter, column names can be added to the matrix:

m<-matrix(c(1,2,3,4,5,6), nrow=2, ncol=3,byrow=TRUE,dimnames=list(c('Obs1', 'Obs2'), c('col1', 'Col2','Col3')))
m
##      col1 Col2 Col3
## Obs1    1    2    3
## Obs2    4    5    6

There are three more alternatives to creating matrices:

rbind(1:3,4:6,10:12)
##      [,1] [,2] [,3]
## [1,]    1    2    3
## [2,]    4    5    6
## [3,]   10   11   12
cbind(1:3,4:6,10:12)
##      [,1] [,2] [,3]
## [1,]    1    4   10
## [2,]    2    5   11
## [3,]    3    6   12
m<-array(c(1,2,3,4,5,6), dim=c(2,3))
m
##      [,1] [,2] [,3]
## [1,]    1    3    5
## [2,]    2    4    6