Adding Id number using group_by() in R

Question

I have a data frame that's formatted like so:

evaluation	grouping
1.00	a
0.50	a
2.00	b
1.00	b
2.00	b
0.50	c

I want to create a new column with ID numbers for each grouping like so:

evaluation	grouping	id
1.00	a	1
0.50	a	1
2.00	b	2
1.00	b	2
2.00	b	2
0.50	c	3

I have attempted this code:

data$id <- data %>% group_by(grouping) %>% 1:nrow(data) %>% ungroup

I think the canonical method would be to use `dplyr::cur_group_id`, as PaulS's (currently-deleted) answer shows. For instance, `df %>% group_by(grouping) %>% mutate(id = cur_group_id())` will give you your expected output. — r2evans, Aug 02 '22 at 11:55

score 1 · Accepted Answer · answered Aug 02 '22 at 11:34

You can do this without group_by.

df %>%
  mutate(ID = match(grouping, unique(grouping)))
#>   evaluation grouping ID
#> 1        1.0        a  1
#> 2        0.5        a  1
#> 3        2.0        b  2
#> 4        1.0        b  2
#> 5        2.0        b  2
#> 6        0.5        c  3

Adding Id number using group_by() in R

1 Answers1