Converting from list to matrix doesn't change the result of typeof function

Question

Here's an example:

t <- list(a=1,b=2,c=3)
typeof(as.matrix(t))

If you run this in R (i'm using ubunutu R version 4.3.1), the typeof is still list. And if you make a matrix like matrix(c(1,2,3), ncol=3) the typeof would return matrix. For another function, I require the type to be a matrix and it's throwing an error otherwise.

I'm not sure if this is a bug or an intended feature but I'd love if someone could explain what's going on. I know I can solve this by calling unlist() and matrix() but I'd be interested to know why this is happening and if perhaps there's some easier way to solve this

Answer 1

as has been discussed in the commens as.matrix is using as.matrix.default method in both cases.

We can chase the differences down further but perhaps its enough to recognise that the base::array function treats a named list input differently to a named vector input.

> str(array(list(a=1,b=2)))
List of 2
 $ : num 1
 $ : num 2
 - attr(*, "dim")= int 2

> str(array(c(a=1,b=2)))
 num [1:2(1d)] 1 2

as.matrix is a wrapper around the underlying array() call