Calculate days since last event, grouped per ID in R

问题

Have a look at the MWE below:

df <- data.frame(date=as.Date(c("06/07/2000","15/09/2000","15/10/2000","03/01/2001","17/03/2001","23/05/2001","26/08/2001"), "%d/%m/%Y"), 
event=c(0,0,1,0,1,1,0))

id       date event
01 2000-07-06     0
01 2000-09-15     0 
01 2000-10-15     1
01 2001-01-03     0
02 2001-03-17     1
02 2001-05-23     1
02 2001-08-26     0
02 2001-08-28     0
03 2001-08-29     1
03 2001-09-05     1
03 2001-09-30     0
03 2001-10-12     1

I want, grouped per ID, the number of days since the last event. My question is similar to this one. Only, I want the result grouped per ID:

id       date event   tae
01 2000-07-06     0   NA
01 2000-09-15     0   NA
01 2000-10-15     1   0 
01 2001-01-03     0   80
02 2001-03-17     1   0
02 2001-05-23     1   67
02 2001-08-26     0   95
02 2001-08-28     0   97
03 2001-08-29     1   0 
03 2001-09-05     1   7
03 2001-09-30     0   25
03 2001-10-12     1   38

I tried the following:

I tried using the steps proposed in the link in a ddply function as below. But this does not seem to do the job.

ddply(df, .(id), transform, last_event_index <- cumsum(df$event) + 1))
ddply(df, .(id), transform, last_event_index <- c(1, last_event_index[1:length(last_event_index) - 1]))
df<- ddply(operationaltemp, .(id), transform, last_event_date =  df[which(df$event==1), "date"])[df$last_event_index])

I hope somebody knows how this can be done.

来源：https://stackoverflow.com/questions/33958035/calculate-days-since-last-event-grouped-per-id-in-r