programmatically rename columns in dplyr

Question

I can rename column in dplyr like this:

mtcars %>% dplyr::rename('cylinder'=cyl)

However, if I would like to change column names programmatically like below:

cnames=c('cylinder', 'mile_per_gallon')
mtcars %>% dplyr::rename(cnames[1]=cyl)
# or like this
mtcars %>% dplyr::rename( !!sym(cnames[1])=cyl)

I got error message:

Error: unexpected '=' in "mtcars %>% dplyr::rename(cnames[1]="

I do not understand why this happens. Does anyone know how to make it work? Thanks.

Answer 1

To programatically setting variable you need to use special operator := and !! to evaluate your variable.

See dplyr's vignette Programming with dplyr

cnames=c('cylinder', 'mile_per_gallon')
library(dplyr, warn.conflicts = F)
mtcars %>% 
  as_tibble() %>%
  rename(!!cnames[1] := cyl)
#> # A tibble: 32 x 11
#>      mpg cylinder  disp    hp  drat    wt  qsec    vs    am  gear  carb
#>  * <dbl>    <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl>
#>  1  21          6  160    110  3.9   2.62  16.5     0     1     4     4
#>  2  21          6  160    110  3.9   2.88  17.0     0     1     4     4
#>  3  22.8        4  108     93  3.85  2.32  18.6     1     1     4     1
#>  4  21.4        6  258    110  3.08  3.22  19.4     1     0     3     1
#>  5  18.7        8  360    175  3.15  3.44  17.0     0     0     3     2
#>  6  18.1        6  225    105  2.76  3.46  20.2     1     0     3     1
#>  7  14.3        8  360    245  3.21  3.57  15.8     0     0     3     4
#>  8  24.4        4  147.    62  3.69  3.19  20       1     0     4     2
#>  9  22.8        4  141.    95  3.92  3.15  22.9     1     0     4     2
#> 10  19.2        6  168.   123  3.92  3.44  18.3     1     0     4     4
#> # ... with 22 more rows

Answer 2

The simplest solution currently to programmatically rename in dplyr is to use the tripple bang (!!!)

library(dplyr)
cnames = c('cylinder' = 'cyl', 'mile_per_gallon' = 'mpg')
mtcars %>% rename(!!!cnames)

Answer 3

Another current solution is using all_of

library(dplyr)
cnames = c('cylinder' = 'cyl', 'mile_per_gallon' = 'mpg')
mtcars %>% rename(all_of(cnames))