Subsetting a data.frame given some criteria

Question

How do I return only the Heights which satisfy an Age criterion in R?

i.e

Age Height 
1   0.5
1   0.6
1   0.7
1   0.6
4   2.0
4   2.3
4   2.3

I want only the heights which correspond to an Age == 4. Which function in R would allow me to do that?

Answer 1

Try this one:

dat <- data.frame(Age=c(1,1,1,1,4,4,4),Height=c(0.5,0.6,0.7,0.6,2.0,2.3,2.3))

dat[dat$Age==4,2]

Answer 2

Also, since you used "subset" in your question title, you could use that command. See ?subset and you'll find that subset(dat, Age == 4, select = "Height") works too.