If there is the same nrows cbind two datas

Question

How to tell R to cbind two matrix only if they have the same number of rows ?

I know that I can check it manually.

Answer 1

Make a function, like:

ckbind = function (a, b) 
{
    a = as.matrix(a)
    b = as.matrix(b)
    if (nrow(a) == nrow(b)) {
        return(cbind(a, b))
    } else {
        stop("Differing number of rows")
    }
}

Note the matrix conversion so it works with vectors. Test:

> ckbind(1:3,2:4)
     [,1] [,2]
[1,]    1    2
[2,]    2    3
[3,]    3    4
> ckbind(1:3,2:6)
Error in ckbind(1:3, 2:6) : Differing number of rows

and check it works with matrices:

> ckbind( ckbind(1:3,2:4), ckbind(3:5,4:6))
     [,1] [,2] [,3] [,4]
[1,]    1    2    3    4
[2,]    2    3    4    5
[3,]    3    4    5    6