Group by, combine and list into a new column in R

January 21, 2023

I have the following dataframe:

df <- data.frame(name = c("michael", "michael", "michael", "jim", "jim", "pam", "dwight", "dwight", "dwight"),
           thing = c("mug", "bandana", "tiny tv", "pranks", "face", "reception", "bear", "beets", "battlestar galactica"))

I would like to group "thing" by "name" and add it to a new column. This column must to be a list type which each element of "thing" correspond to an element of this list.

I’ve tried this:

df_1 <- df %>% group_by(name) %>% 
  mutate(new_col = paste0(as.list(thing), collapse = "\", \"")) %>% 
  mutate(new_col = paste0("c('", new_col)) %>%
  mutate(new_col= as.list(str_trim(new_col, side = "both"))) %>% 
  ungroup() %>% 
  select(-thing)

df_1$new_col <- as.list(paste(df_1$new_col, "\")", sep = ""))

df_1 <- as.tibble(unique(df_1))

# A tibble: 4 × 2
  name    new_col  
  <chr>   <list>   
1 michael <chr [1]>
2 jim     <chr [1]>
3 pam     <chr [1]>
4 dwight  <chr [1]>

However, I want this:

# A tibble: 4 × 2
  name    new_col  
  <chr>   <list>   
1 michael <chr [3]>
2 jim     <chr [2]>
3 pam     <chr [1]>
4 dwight  <chr [3]>

Thank you in advance.

>Solution :

A list-column shouldn’t need to use paste or similar, we can do just

out <- df %>%
  group_by(name) %>%
  summarize(new_col = list(thing))
out
# # A tibble: 4 × 2
#   name    new_col  
#   <chr>   <list>   
# 1 dwight  <chr [3]>
# 2 jim     <chr [2]>
# 3 michael <chr [3]>
# 4 pam     <chr [1]>
out$new_col[[1]]
# [1] "bear"                 "beets"                "battlestar galactica"

Note that there is also

df %>%
  group_nest(name, .key = "new_col")
# # A tibble: 4 × 2
#   name               new_col
#   <chr>   <list<tibble[,1]>>
# 1 dwight             [3 × 1]
# 2 jim                [2 × 1]
# 3 michael            [3 × 1]
# 4 pam                [1 × 1]

in which each of new_col is an embedded frame, each of which here has just one column:

out <- df %>%
  group_nest(name, .key = "new_col")
out$new_col[[1]]
# # A tibble: 3 × 1
#   thing               
#   <chr>               
# 1 bear                
# 2 beets               
# 3 battlestar galactica