Quick question about subsetting via character-class

Question

I think this is a super quick thing, but I figured I\'d ask since I can\'t for the life of me remember how to do it...

Suppose, I have a data.frame (call it, DF

Answer 1

DF$foo[1] tries to return the first element of the column named foo (which doesn't exist). You want DF[foo[1]].

Answer 2

subset(DF, select=foo[3])
              Blah
1   0.814939149951
2  -0.800644571486
3  -0.424080059851
4   1.012792429940
5   1.291888735720
6   0.642523425131
7   0.537486547429
8   0.315031122082
9  -0.296439716108
10  0.372453578695

Answer 3

Is this what you want?

DF[ ,foo][1]

Ah, Joshua posted while I was typing... You can aslo select regions of the columns, eg:

DF[1:3,foo][1]