Odp: Matrix

Hi

r-help-bounces at r-project.org napsal dne 02.02.2009 16:52:06:

Hi,

I have a very basic question on merging two matrices by alternating the
rows. For illustration, assume two matrices -

A looks like:

10 10
10 10

B looks like:

20 20
20 20

How do I combine them such that I get alternating rows from A and B? My
final result should be C which looks like:

10 10
20 20
10 10
20 20

I would rbind both matrices and then indexed the resulting matrix.

x<-rep(10,4)
y<-rep(20,4)
dim(x)<-c(2,2)
dim(y)<-c(2,2)
z<-rbind(x,y)

z

    [,1] [,2]
[1,]   10   10
[2,]   10   10
[3,]   20   20
[4,]   20   20

ind<-c(seq(1,4,2), seq(2,4,2))
z[ind,]

z[ind,]

    [,1] [,2]
[1,]   10   10
[2,]   20   20
[3,]   10   10
[4,]   20   20