Enter new column names as string in dplyr's rename function

Question

dplyr's rename functions require the new column name to be passed in as unquoted variable names. However I have a function where the column name is constructed by pasting a string onto an argument passed in and so is a character string.

For example say I had this function

myFunc <- function(df, col){
  new <- paste0(col, '_1')
  out <- dplyr::rename(df, new = old)
  return(out)
}

If I run this

df <- data.frame(a = 1:3, old = 4:6)
myFunc(df, 'x')

I get

  a new
1 1   4
2 2   5
3 3   6

Whereas I want the 'new' column to be the name of the string I constructed ('x_1'), i.e.

  a x_1
1 1   4
2 2   5
3 3   6

Is there anyway of doing this?

Answer 1

I think this is what you were looking for. It is the use of rename_ as @Henrik suggested, but the argument has an, lets say, interesting, name:

> myFunc <- function(df, col){
+   new <- paste0(col, '_1')
+   out <- dplyr::rename_(df, .dots=setNames(list(col), new))
+   return(out)
+ }
> myFunc(data.frame(x=c(1,2,3)), "x")
  x_1
1   1
2   2
3   3
>

Note the use of setNames to use the value of new as name in the list.

Answer 2

Recent updates to tidyr and dplyr allow you to use the rename_with function.

Say you have a data frame:

library(tidyverse)

df <- tibble(V0 = runif(10), V1 = runif(10), V2 = runif(10), key=letters[1:10])

And you want to change all of the "V" columns. Usually, my reference for columns like this comes from a json file, which in R is a labeled list. e.g.,

colmapping <- c("newcol1", "newcol2", "newcol3")
names(colmapping) <- paste0("V",0:2)

You can then use the following to change the names of df to the strings in the colmapping list:

df <- rename_with(.data = df, .cols = starts_with("V"), .fn = function(x){colmapping[x]})