Adding unique ID column associated to two groups R

Question

I have a data frame in this format:

Group	Observation
a	1
a	2
a	3
b	4
b	5
c	6
c	7
c	8

I want to create a unique ID column which considers both group and each unique observation within it, so that it is formatted like so:

Group	Observation	Unique_ID
a	1	1.1
a	2	1.2
a	3	1.3
b	4	2.1
b	5	2.2
c	6	3.1
c	7	3.2
c	8	3.3

Does anyone know of any syntax or functions to accomplish this? The formatting does not need to exactly match '1.1' as long as it signifies group and each unique observation within it. Thanks in advance

score 2 · Accepted Answer · answered Jul 12 '22 at 10:59

Another way using cur_group_id and row_number

library(dplyr)

A <- 'Group Observation
a   1
a   2
a   3
b   4
b   5
c   6
c   7
c   8'

df <- read.table(textConnection(A), header = TRUE)

df |> 
  group_by(Group) |> 
  mutate(Unique_ID = paste0(cur_group_id(), ".", row_number())) |> 
  ungroup()

  Group Observation Unique_ID
  <chr>       <int> <chr>    
1 a               1 1.1      
2 a               2 1.2      
3 a               3 1.3      
4 b               4 2.1      
5 b               5 2.2      
6 c               6 3.1      
7 c               7 3.2      
8 c               8 3.3

score 0 · Answer 2 · answered Jul 12 '22 at 10:54

library(tidyverse)

df <- read_table("Group Observation
a   1
a   2
a   3
b   4
b   5
c   6
c   7
c   8")

df %>%
  mutate(unique = Group %>%
           as.factor() %>%
           as.integer() %>% 
           paste(., Observation, sep = "."))

#> # A tibble: 8 x 3
#>   Group Observation unique
#>   <chr>       <dbl> <chr> 
#> 1 a               1 1.1   
#> 2 a               2 1.2   
#> 3 a               3 1.3   
#> 4 b               4 2.4   
#> 5 b               5 2.5   
#> 6 c               6 3.6   
#> 7 c               7 3.7   
#> 8 c               8 3.8

^{Created on 2022-07-12 by the reprex package (v2.0.1)}

score 0 · Answer 3 · answered Jul 12 '22 at 11:04

Try this

df |> group_by(Group) |>
mutate(Unique_ID = paste0(cur_group_id(),".",1:n()))

output

# A tibble: 8 × 3
# Groups:   Group [3]
  Group Observation Unique_ID
  <chr>       <int> <chr>    
1 a               1 1.1      
2 a               2 1.2      
3 a               3 1.3      
4 b               4 2.1      
5 b               5 2.2      
6 c               6 3.1      
7 c               7 3.2      
8 c               8 3.3

Adding unique ID column associated to two groups R

3 Answers3