r - Getting the column names of a Data Frame with sapply

Question

I want to get the columns names of a Data Frame with the following code:

DF <- data.frame(X=c(1,2), Y=c(3,4))
as.character(sapply(DF, names))

I've got the following:

"NULL" "NULL"

but I need the following result:

"X" "Y" 

How can I do this, thanks in advance.

Answer 1

But there's a function to do it directly. See ?colnames

colnames(DF)
[1] "X" "Y"

In this case you could also do

names(DF)
[1] "X" "Y"

either way you don't need sapply to extract the column names.

If you name the rows names still only gives the column names:

rownames(DF)<-list("a","b")
DF
  X Y
a 1 3
b 2 4
names(DF)
[1] "X" "Y"

but the rownames function gets the row names for you:

rownames(DF)
[1] "a" "b"

If you had a list of data frames with the same number of columns you might perhaps use sapply with names.

If you want to obtain both the row and column names of the data frame, see dimnames.