How to convert a string in a function into an object?

Question

I would like to convert a string that I pass in a function into an object (or column name).

I know that this works:

df <- data.frame(A = 1:10, B =         


        

Answer 1

The trick is to use parse. For instance:

> x <- "A"
> eval(parse(text=paste("df$", x, sep = "")))
 [1]  1  2  3  4  5  6  7  8  9 10

See also this Q/A: Evaluate expression given as a string