refer to range of columns by name in R

Question

I need help with something that might be fairly simple in R. I want to refer to a range of columns in a data frame (e.g., extracting a few select variables). However, I don\

Answer 1

You can call the column numbers by their names:

set.seed(1234)
> mydf <- data.frame(A = runif(5, 1, 2),
                     + B = runif(5, 3, 4),
                     + C = runif(5, 5, 6),
                     + D = runif(5, 7, 8),
                     + E = runif(5, 9, 10))
> mydf
mydf[c(match("A", names(mydf)):match("B", names(mydf)))]
         A        B
1 1.113703 3.640311
2 1.622299 3.009496
3 1.609275 3.232551
4 1.623379 3.666084
5 1.860915 3.514251

Here you can see that the match()-call actually gives the column number:

> c(match("A", names(mydf)):match("B", names(mydf)))
[1] 1 2

I hope this is also helpful, it is similar to Neal's answer.