Make column with lists of characters that match a second column in R

I have a data frame in R with 2 columns, each of which has repeat values.

df <- data.frame(item  = c("X", "Y", "Z", "X", "Z"),
                  label = c("ABC", "DEF", "DEF", "GHI", "ABC"))

 item label
1    X   ABC
2    Y   DEF
3    Z   DEF
4    X   GHI
5    Z   ABC

I’d like to transform it so that I have a unique row for each label and a column that lists all the items that match it separated by commas. So something like this:

 label items
1   ABC  X, Z
2   DEF  Y, Z
3   GHI     X

I’ve tried using spread and aggregate, but I haven’t been able to land on something that works. Does anyone have suggestions? Thanks!

>Solution :

We could use toString:

library(dplyr)

df %>% 
  group_by(label) %>% 
  summarise(item = toString(item))

  label item 
  <chr> <chr>
1 ABC   X, Z 
2 DEF   Y, Z 
3 GHI   X    
``´