> data <- data.frame(x=1:3,y=4:6,z=7:9)
> data[c("x","y")]
x y
1 1 4
2 2 5
3 3 6
> mylist <- c("x","y")
> data[mylist]
x y
1 1 4
2 2 5
3 3 6
> data[,mylist]
x y
1 1 4
2 2 5
3 3 6
>I'd generally use the second form of subsetting above (i.e., data[,mylist], because that will work with matrices as well).
hope this helps,
Tony Plate
At Thursday 01:22 PM 7/29/2004, Peter Wilkinson wrote:
This seems like such a trivial thing to do:
given a data.frame DF and variables w,v, x,y,z I can do
DF["x"] or DF[c("x","y")]
if I create a vector, mylist = c("x",y")
then I do DF[mylist]
I am not getting x and y, I get something else.
what is the correct way to subset a data.frame by columns using a vector, as if I were doing DF["x","y"]?
Peter
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