### Using dplyr::rename() within a function

#### June 10, 2020    tibbledplyr

Today I rewrote some old code and came across something that I thought I would write down because I’m pretty sure I’ll forget it if I don’t! The issue was passing strings to the rename() function from the dplyr package to rename a column. This came about because of a change in a older1 version of dplyr which had functions specifically for use inside your own functions. These had an underscore as a postfix. So instead of using rename() I was using rename_(). There are now depreciated and so I was updating my code.

It was a pretty simple function but still created a few errors until I found the necessary bit in the documentation. More on that in a minute, first let’s create some data and see what we’re trying to do.

library(dplyr)
temp <- tribble(
~x, ~y,
1, 2,
3, 4
)
temp
# A tibble: 2 x 2
x     y
<dbl> <dbl>
1     1     2
2     3     4

Now we’ve got some data we can rename() a column.

rename(temp, x2 = x)
# A tibble: 2 x 2
x2     y
<dbl> <dbl>
1     1     2
2     3     4

So far so good. However, things get a little trickier if you want to do this inside another function. For example we could try this function.

my_rename <- function(dat_f, new_name) {
rename(dat_f, new_name = x)
}

We can try using this with a string and without.

my_rename(temp, "x2")
# A tibble: 2 x 2
new_name     y
<dbl> <dbl>
1        1     2
2        3     4
my_rename(temp, x2)
# A tibble: 2 x 2
new_name     y
<dbl> <dbl>
1        1     2
2        3     4

Not quite what we were looking for and it doesn’t produce an error. After a little looking I found the necessary information on the use of tidy selection in rename() - you can read it here. With the new info we can rewrite the function to use glue notation and assignment with the := operator. This works with and without quotes.

my_rename <- function(dat_f, new_name) {
rename(dat_f, {{new_name}} := x)
}
my_rename(temp, "x2")
# A tibble: 2 x 2
x2     y
<dbl> <dbl>
1     1     2
2     3     4
my_rename(temp, x3)
# A tibble: 2 x 2
x3     y
<dbl> <dbl>
1     1     2
2     3     4

In a future post I plan to do a run through (mainly for myself when I forget things) a few things like this including quosures.

1. much older↩︎