In R: pass column name as argument and use it in function with dplyr::mutate() and lazyeval::interp()

Question

This question links to this SO answer except that here I want to use the variable specified as function arg in a mutate_(). It works if I don\'t make any \"calc

Answer 1

You have to use lazy evaluation (with the package lazyeval), for example like this:

library(lazyeval)
func2 <- function(df, varname){
     df %>%
       mutate_(v3=interp(~sum(x), x = as.name(varname)))
}
func2(data, "v1")
#  v1 v2 v3
#1  1  3  3
#2  2  4  3