How to add a new column to an R matrix

Question

I want to add a new column to an existing matrix. Which R function should I use?

Answer 1

You can use the cbind() function to add a new column to an R matrix. The number of rows in the new column should match the existing matrix. If the existing matrix has k rows, the new column should also have k rows.

Here is an example:

I have created a matrix 'mm' with 5 rows and 4 columns.

mm <- matrix(c(1:20), ncol = 4, nrow = 5)
mm <- cbind(mm, c(21:25))

The old value of 'mm':

> mm
     [,1] [,2] [,3] [,4]
[1,]    1    6   11   16
[2,]    2    7   12   17
[3,]    3    8   13   18
[4,]    4    9   14   19
[5,]    5   10   15   20

The new value of 'mm':

> mm
     [,1] [,2] [,3] [,4] [,5]
[1,]    1    6   11   16   21
[2,]    2    7   12   17   22
[3,]    3    8   13   18   23
[4,]    4    9   14   19   24
[5,]    5   10   15   20   25