Question

I’m using cbind to bring together a matrix of string and numerics, and it is returning all of the columns of numerics (except the first one) as NULL. Here is sample code:

nums <- matrix(data=c(1,2,3,4),ncol=2)
strs <- list()
strs[1] <- 'row1'
strs[2] <- 'row2'
result <- cbind(strs,nums)

> result
     strs         
[1,] "row1" 1 NULL
[2,] "row2" 2 NULL

I’m obviously overlooking something simple. Thanks for the help,

Answer 1

In this case, I think you’re going about the problem in slightly the wrong way. cbind returns a matrix. One of the limitations of matrices is that all elements must be of the same type. This means your c(1, 2, 3, 4) will, when coerced into a matrix, become the highest level data type present (in this case character from strs) and become the equivalent of c("1", "2", "3", "4").

I’m going to assume that you have a list strs with 2 elements and that what you actually want is a data.frame (which is able to hold different types).

In either case, let’s convert strs into a character first:

strs2 <- unlist(strs)
[1] "row1" "row2"

Note that this is the same as if you’d created it via c("row1", "row2").
Next, we’ll create a data.frame:

result <- data.frame(strs2, nums)
  strs2 X1 X2
1 row1   1  3
2 row2   2  4

This is essentially the same solution that @thelatemail provided.