You’d need to be a bit more specific.

In general, just try out different things to see what they do. Here are some examples:

> a+b
     [,1] [,2] [,3]
[1,]    5    7    9
[2,]    5    7    9
[3,]    5    7    9
[4,]    5    7    9
> c(a,b)
 [1] 1 1 1 1 2 2 2 2 3 3 3 3 4 4 4 4 5 5 5 5 6 6 6 6
> matrix(c(a,b),4)
     [,1] [,2] [,3] [,4] [,5] [,6]
[1,]    1    2    3    4    5    6
[2,]    1    2    3    4    5    6
[3,]    1    2    3    4    5    6
[4,]    1    2    3    4    5    6
> cbind(a,b)
     [,1] [,2] [,3] [,4] [,5] [,6]
[1,]    1    2    3    4    5    6
[2,]    1    2    3    4    5    6
[3,]    1    2    3    4    5    6
[4,]    1    2    3    4    5    6
> rbind(a,b)
     [,1] [,2] [,3]
[1,]    1    2    3
[2,]    1    2    3
[3,]    1    2    3
[4,]    1    2    3
[5,]    4    5    6
[6,]    4    5    6
[7,]    4    5    6
[8,]    4    5    6

I need to learn about :
the combine of two matrices.

thanke you very much
Jafari

I’m surprised someone is actually reading this blog :)

rbind combines a and b row by row. Then matrix goes column by column through the old rbind(a,b) matrix to pick the values that form the new matrix with just four rows.

Before I found rbind, I had this unwieldy solution:

matrix(t(matrix(c(t(a),t(b)),3)),4)

where t(matrix(c(t(a),t(b)),3)) does what rbind(a,b) does.