crazybilly crazybilly - 2 months ago 8
R Question

How to pass a named vector to dplyr::select using quosures?

Using the old

select_()
function, I could pass a named vector into select and change position and column names at once:

my_data <- data_frame(foo = 0:10, bar = 10:20, meh = 20:30)
my_newnames <- c("newbar" = "bar", "newfoo" = "foo")

move_stuff <- function(df, newnames) {
select_(df, .dots = newnames)
}

move_stuff(my_data, newnames = my_newnames) )

# this is the desired output
# A tibble: 4 x 2
newbar newfoo
<int> <int>
1 10 0
2 11 1
3 12 2
4 13 3


I tried doing something similar using quosures and splicing--selecting columns works great, but the names of the vectors (and thus renaming columns at the same time) seems to be ignored. Both of the following return data frames with columns named
bar
and
foo
, but not
newbar
and
newfoo
:

move_stuff2 <- function(df, newnames) {
select(df, !!!newnames)
}

# returns df with columns bar and foo
move_stuff2(my_data, quo(my_newnames))
move_stuff2(my_data, quos(my_newnames))


Is there a way to use a named vector using the new NSE methodology to both rename and reorder columns?

Answer Source

quo (or quos for multiple) is for unquoted variable names, not strings. To convert strings to quosures use sym (or syms), and use !! or !!! as appropriate to unquote or unquote-splice:

library(dplyr)

my_data  <- data_frame(foo = 0:10, bar = 10:20, meh = 20:30)
my_newnames  <-  c("newbar" = "bar", "newfoo" = "foo")

For strings,

move_stuff_se <- function(df, ...){
     df %>% select(!!!rlang::syms(...))
}

move_stuff_se(my_data, my_newnames)
#> # A tibble: 11 x 2
#>    newbar newfoo
#>     <int>  <int>
#>  1     10      0
#>  2     11      1
#>  3     12      2
#>  4     13      3
#>  5     14      4
#>  6     15      5
#>  7     16      6
#>  8     17      7
#>  9     18      8
#> 10     19      9
#> 11     20     10

For unquoted variable names,

move_stuff_nse <- function(df, ...){
    df %>% select(!!!quos(...))
}

move_stuff_nse(my_data, newbar = bar, newfoo = foo)
#> # A tibble: 11 x 2
#>    newbar newfoo
#>     <int>  <int>
#>  1     10      0
#>  2     11      1
#>  3     12      2
#>  4     13      3
#>  5     14      4
#>  6     15      5
#>  7     16      6
#>  8     17      7
#>  9     18      8
#> 10     19      9
#> 11     20     10