How do I use tidyverse select when the column is input as a character object?

Question

I'm trying to create a function which selects columns based on the input to a function:

f <- function(string) {
  quosure <- quo(!!sym(string))
  dplyr::select(data, !!quosure)
}
temp <- f("id") # returns " Error in !quosure : invalid argument type"

Strangely, this very similar looking code seems to work.

g <- function(string) {
  quosure <- quo(!!sym(string))
  dplyr::pull(data, !!quosure)
}
temp <- g("id") # Works fine

What is the difference between the first and the second function which means that the first fails and the second works?

Answer 1

It works fine for me with dplyr version '0.8.0.1'.

library(dplyr)
packageVersion("dplyr")
'0.8.0.1'

data <- data.frame(id= 1:10, othervariable= 11:20)
f <- function(string) {
  quosure <- quo(!!sym(string))
  dplyr::select(data, !!quosure)
}
temp <- f("id")
temp
id
1   1
2   2
3   3
4   4
5   5
6   6
7   7
8   8
9   9
10 10

And if you need to select (multiple) column(s) from a dataframe with a vector of characters I would rather do

df <- data.frame(id= 1:10, othervariable= 11:20, x= 21:30)
f <- function(data, string) {
  data[ , string]
}
temp <- f(data= df, string= c("id", "x"))
temp
   id  x
1   1 21
2   2 22
3   3 23
4   4 24
5   5 25
6   6 26
7   7 27
8   8 28
9   9 29
10 10 30