Maintain original column titles with dplyr function in loop R - r

Question

Let's say I have a dataset like mtcars and I would like to loop over different columns to calculate counts (among others).
library(dplyr)
df <- mtcars
groups <- c('cyl', 'hp')
for(g in groups) {
group_counts <- df %>%
group_by(get(g)) %>%
count()
print(group_counts)
}
Which gives me the following for the cyl column and something similar for the hp column:
`get(g)` n
4 11
6 7
8 14
How do I manage to the first column to return the original column name instead of the 'get(g)'? Like this
cyl n
4 11
6 7
8 14

Answer 1

You can use across(all_of()) like this:
for(g in groups) {
group_counts <- df %>%
group_by(across(all_of(g))) %>%
count()
print(group_counts)
}
Output:
# A tibble: 3 × 2
# Groups: cyl [3]
cyl n
<dbl> <int>
1 4 11
2 6 7
3 8 14
# A tibble: 22 × 2
# Groups: hp [22]
hp n
<dbl> <int>
1 52 1
2 62 1
3 65 1
4 66 2
5 91 1
6 93 1
7 95 1
8 97 1
9 105 1
10 109 1
# … with 12 more rows

Answer 2

groups is a character vector. To reference objects with corresponding names, we can convert to symbol and evaluate !!:
for(g in groups) {
group_counts <- df %>%
group_by(!!sym(g)) %>%
count()
print(group_counts)
}
# A tibble: 3 × 2
# Groups: cyl [3]
cyl n
<dbl> <int>
1 4 11
2 6 7
3 8 14
# A tibble: 22 × 2
# Groups: hp [22]
hp n
<dbl> <int>
1 52 1
2 62 1
3 65 1
4 66 2
5 91 1
6 93 1
7 95 1
8 97 1
9 105 1
10 109 1
# … with 12 more rows
# ℹ Use `print(n = ...)` to see more rows
We can also convert groups into a vector of symbols outside the loop, and evaluate !! inside the loop:
my_function <- function(df, groups) {
groups <- syms(groups)
for(g in groups) {
group_counts <- df %>%
group_by(!!g) %>%
count()
print(group_counts)
}
}
my_function(df, groups)
# A tibble: 3 × 2
# Groups: cyl [3]
cyl n
<dbl> <int>
1 4 11
2 6 7
3 8 14
# A tibble: 22 × 2
# Groups: hp [22]
hp n
<dbl> <int>
1 52 1
2 62 1
3 65 1
4 66 2
5 91 1
6 93 1
7 95 1
8 97 1
9 105 1
10 109 1
# … with 12 more rows
# ℹ Use `print(n = ...)` to see more rows