r - how to subtract first date entry from last date entry in grouped data and control output format

Question

This question is very similar to a question asked in another thread which can be found here. I\'m trying to achieve something similar: within groups (events) subtract the first

Answer 1

We can use difftime and specify the unit to get all the difference in the same unit.

df %>% 
   group_by(event) %>% 
   summarise(First = first(time),
             Last = last(time) , 
             difference= difftime(last(time), first(time), unit='hour'))