从data.table聚合（R语言）

Question

I have a data table myTable like this(input):

user_id    timestamp  event_id

1 Ann      11115555   Level1Start
2 Serg     11113333   Level1Start
3 Ann      11117777   Level1Complete
4 Ann      11116666   Level1Complete
5 Ann      11112222   Level1Start

I need to add the column named timeInLevel and calculate time between first two logs Level1Start and Level1Complete.

Output:

user_id    timestamp  event_id         TimeInLevel

1 Ann      11115555   Level1Start      4444
2 Serg     11113333   Level1Start      NA
3 Ann      11117777   Level1Complete   4444
4 Ann      11116666   Level1Complete   4444
5 Ann      11112222   Level1Start      4444

THX for help!!!

Answer 1

Perhaps something like this using data.table syntax:

dt[, TimeInterval := min(timestamp[event_id == "Level1Complete"]) - 
     min(timestamp[event_id == "Level1Start"]), by = user_id]
#   user_id timestamp       event_id TimeInterval
#1:     Ann  11115555    Level1Start         4444
#2:    Serg  11113333    Level1Start           NA
#3:     Ann  11117777 Level1Complete         4444
#4:     Ann  11116666 Level1Complete         4444
#5:     Ann  11112222    Level1Start         4444