Passing a variable name to a function in R

Question

I\'ve noticed that quite a few packages allow you to pass symbol names that may not even be valid in the context where the function is called. I\'m wondering how this works

Answer 1

I've recently discovered what I think is a better approach to passing variable names.

a <- data.frame(x = 1:10, y = 1:10)

b <- function(df, name){
    eval(substitute(name), df)
}

b(a, x)
  [1]  1  2  3  4  5  6  7  8  9 10

Update The approach uses non standard evaluation. I began explaining but quickly realized that Hadley Wickham does it much better than I could. Read this http://adv-r.had.co.nz/Computing-on-the-language.html