Assign names to data frame with as.data.frame function

Question

I am trying to convert a matrix into data frame, and assign the names in one line.

As I used ?as.data.frame there is a parameter called col.names which doesn't seem to work for me, am I doing something wrong?

as.data.frame(matrix(c(1:4), nrow=2), col.names=c("a","b"))

Output:

   V1 V2  
1  1  3  
2  2  4  

Expected Output:

   a  b  
1  1  3  
2  2  4  

I know I can assign it later with `colnames(matrix) = c("a,"b), but i am just wondering if it is possible to do it in one line. (

Answer 1

We can use dimnames argument in matrix and this will return with the column names as such when converting to data.frame

as.data.frame(matrix(1:4, nrow=2, dimnames = list(NULL, c("a", "b"))))
#  a b
#1 1 3
#2 2 4

while in the OP's code, the matrix output didn't have any column names, so as.data.frame creates column names as 'V1', 'V2' by default. The col.names argument is not as.data.frame for class matrix, so it didn't have any effect

If we quote the documentation of ?as.data.frame

S3 method for class 'matrix'

as.data.frame(x, row.names = NULL, optional = FALSE, ..., stringsAsFactors = default.stringsAsFactors())

Answer 2

I know that it's an old question, but is:

as.data.frame %>% colnames<-("Name here") not also a solution in 'one line' as the original poster wanted, but just with pipes?

All the best, Patrick