Construct variable names in select_

Question

I am trying to write a function that will (in part) rename a variable by combining its source dataframe and existing variable name. In essence, I want:

df1 <- data.frame(a = 1, b = 2)

to become:

df1 %>%
  rename(df1_a = a)

#  df1_a b
#1     1 2

But I want to do this programatically, something along the lines of:

fun <- function(df, var) {
  outdf <- rename_(df, paste(df, var, sep = "_") = var)
  return(outdf)
}

This admittedly naive approach obviously doesn't work, but I haven't been able to figure it out. I'm sure the answer is somewhere in the nse vignette (https://cran.r-project.org/web/packages/dplyr/vignettes/nse.html), but that doesn't seem to address constructing variable names.

Answer 1

Not sure if this is the proper dplyr-esque way, but it'll get you going.

fun <- function(df, var) {
    x <- deparse(substitute(df))
    y <- deparse(substitute(var))
    rename_(df, .dots = with(df, setNames(as.list(y), paste(x, y, sep = "_"))))
}

fun(df1, a)
#   df1_a b
# 1     1 2

fun(df1, b)
#   a df1_b
# 1 1     2