How to collapse dataframe rows if entry is the same?

Question

I have a dataframe in R that has repeated entries in column a:

a <- c("cat", "dog", "cat", "dog")
b <- c("siamese", "chow", "burmese", "husky")
dataframe <- data.frame(a,b)

   a       b
1 cat siamese
2 dog    chow
3 cat burmese
4 dog   husky

How do I collapse entries where a is repeated multiple times? For example, to end up with a dataframe like this:

   a       b
1 cat siamese; burmese
2 dog    chow; husky

score 2 · Accepted Answer · answered Apr 27 '20 at 10:37

2

You can use aggregate with paste setting collapse = "; "

aggregate(b ~ a, dataframe, paste, collapse = "; ")
#    a                b
#1 cat siamese; burmese
#2 dog      chow; husky

answered Apr 27 '20 at 10:37

GKi

27,870
2
18
35

score 0 · Answer 2 · answered Apr 27 '20 at 10:38

0

You can simply do :

dataframe %>% 
  group_by(a) %>%
  summarize(b = paste(b, collapse = ", "))

answered Apr 27 '20 at 10:38

Jrm_FRL

1,294
3
14

Error in FUN(X, ...) : argument "FUN" is missing, with no default. Note: I fixed the above error by changing spelling of summarize to summarise – icedcoffee Jun 08 '20 at 14:14

How to collapse dataframe rows if entry is the same?

2 Answers2