Using parameters as col names in dplyr

Question

I am struggling to mix referencing column names using parameters and directly from the dataframe. please help me correct the second function to return the same result as the first

install.packages("dplyr", version = "0.5.0")`
library(dplyr)

df <- data.frame(year = 2010:2015, GVA = 1:6)
f <- function(df) {
  df %>%
  mutate(indexGVA = GVA/max(ifelse(year == 2010, GVA, 0)) * 100)
}
f(df)

g <- function(df, val = NULL) {
  df %>%
  mutate_(indexGVA = ~val/max(ifelse(year == 2010, val, 0)) * 100)
}
g(df, val = "GVA")

Answer 1

mutate_ is now deprecated (?mutate_), you can instead use enquo and !! from rlang to quote and unquote the arguments:

library(rlang)
g <- function(df, val = NULL) {
  val_quo = enquo(val)
  df %>%
    mutate(indexGVA = (!! val_quo)/max(ifelse(year == 2010, (!! val_quo), 0)) * 100)
}

g(df, val = GVA)

Result:

  year GVA indexGVA
1 2010   1      100
2 2011   2      200
3 2012   3      300
4 2013   4      400
5 2014   5      500
6 2015   6      600