R function: Use argument to extract data from other argument

Question

Here is a simple R function:

aa <- function(x, cells, aberrations) {
  return(list(x[[cells]], x[[aberrations]]))
}

So for example if I run this with sample data below, I have

df1 <- data.frame(x = 1:10, y = 11:20)
aa(df1, cells = "x", aberrations = "y")
[[1]]
 [1]  1  2  3  4  5  6  7  8  9 10

[[2]]
 [1] 11 12 13 14 15 16 17 18 19 20

Is there a way, I can extract the data from df1 with something like this?

aa(df1, cells = x, aberrations = y)

That is, not using a character, "x", but just x. I tried this,

aa <- function(x, cells, aberrations) {
  a <- as.character(cells); b <- as.character(aberrations)
  return(list(x[[a]], x[[as.character(b)]]))
}

But did not work.

This idea is inspired by the ggplot function, where I can do this,

ggplot(df1, aes(x, y)) + geom_point()

with no error at all even though x and y are not defined in the workspace, but on the data frame df1.