I am a bit confused. I have a datatable similar to that:
library(data.table)
DT<-data.table(contract=c("c","c","c","d","d","d","d","f","f","f","f"),events=c("a","b","c","a","b","b","c","a","b","c","d"))
contract events
c a
c b
c c
d a
d b
d b
d c
f a
f b
f c
f d
And I would like to count the number of events by contract by keeping track of repetitions, so to end up with something like that:
contract events seqevents
c a 1
c b 2
c c 3
d a 1
d b 2
d b 2
d c 3
f a 1
f b 2
f c 3
f d 4
As a start, I tried to obtain a simple count of events by contract with this code, and then try to figure out a way to account for repetitions of the same event:
DT<-DT[ , seqevents := 1:.N , by = c("contract","events") ]
But the output is not correct, though it worked on a different data set. Any suggestions on why it doesn't work and how can I get a count as illustrated above? Thanks a lot
