The following function behaves as desired: several variables can be passed to group_by without the need to put them into alist() or dplyr::vars:
mean_by_grp <- function(df, meanvar, grp) {
grouping <- enexpr(grp) %>%
expr_deparse %>%
str_split(",",simplify = T) %>% `[`(1,) %>%
map(str_remove,"c\\(") %>% map(str_remove,"\\)") %>% map(str_trim) %>%
unlist %>% syms
df %>%
group_by(!!!syms(grouping)) %>%
summarise("average_{{meanvar}}" := mean({{meanvar}}, na.rm = TRUE),
.groups = 'drop')
}
starwars %>% mean_by_grp(height, species)
starwars %>% mean_by_grp(height, c(species, homeworld))
However, it is complicated. I need to turn c(var1,....varn) into a string, split it and turn it into a list of symbols so I can use with with syms.
Isn't there a much easier way to do this?
Of course, I could use ellipses instead of grp, but then I can only have one argument that passes multiple symbols to another function.
One option would be dplyr::across:
mean_by_grp <- function(df, meanvar, grp) {
df %>%
group_by(across({{ grp }})) %>%
summarise("average_{{meanvar}}" := mean({{meanvar}}, na.rm = TRUE),
.groups = 'drop')
}
library(dplyr)
starwars %>% mean_by_grp(height, species)
#> # A tibble: 38 × 2
#> species average_height
#> <chr> <dbl>
#> 1 Aleena 79
#> 2 Besalisk 198
#> 3 Cerean 198
#> 4 Chagrian 196
#> 5 Clawdite 168
#> 6 Droid 131.
#> 7 Dug 112
#> 8 Ewok 88
#> 9 Geonosian 183
#> 10 Gungan 209.
#> # … with 28 more rows
starwars %>% mean_by_grp(height, c(species, homeworld))
#> # A tibble: 58 × 3
#> species homeworld average_height
#> <chr> <chr> <dbl>
#> 1 Aleena Aleen Minor 79
#> 2 Besalisk Ojom 198
#> 3 Cerean Cerea 198
#> 4 Chagrian Champala 196
#> 5 Clawdite Zolan 168
#> 6 Droid Naboo 96
#> 7 Droid Tatooine 132
#> 8 Droid <NA> 148
#> 9 Dug Malastare 112
#> 10 Ewok Endor 88
#> # … with 48 more rows