r - Adding a matrix to a list -

i r newbie. trying add matrix list before returning function.

a <- matrix(4,4,4) x <- list(l=1, m=2) x["n"] <- 

the above ends following warning message , 1 number matrix gets added list.

warning message: in x["n"] <- :   number of items replace not multiple of replacement length 

how can this? nice if how don't have specify dimensions of matrix before hand.

use $ extraction:

> x$n <- > x $l [1] 1  $m [1] 2  $n      [,1] [,2] [,3] [,4] [1,]    4    4    4    4 [2,]    4    4    4    4 [3,]    4    4    4    4 [4,]    4    4    4    4 

or [[ extraction:

> x$n <- null > x[["n"]] <- > x $l [1] 1  $m [1] 2  $n      [,1] [,2] [,3] [,4] [1,]    4    4    4    4 [2,]    4    4    4    4 [3,]    4    4    4    4 [4,]    4    4    4    4