insert rows between dates by group

Question

I want to insert rows between two dates by group. My way of doing it is so complicated that I insert missing values by last observation carry forwards and then merge. I was wond

Answer 1

A Base R (not quite as elegant) solution:

# Data
user<-c("A","A","B","B","B") 
dummy<-c(1,1,1,1,1)
date<-as.Date(c("2017/1/3","2017/1/6","2016/5/1","2016/5/3","2016/5/5"))
df1 <-data.frame(user,dummy,date)

# Solution
do.call(rbind, lapply(split(df1, df1$user), function(df) {
  dff <- data.frame(user=df$user[1], dummy=0, date=seq.Date(min(df$date), max(df$date), 'day'))
  dff[dff$date %in% df$date, "dummy"] <- df$dummy[1]
  dff
}))


# user dummy date      
# A    1     2017-01-03
# A    0     2017-01-04
# A    0     2017-01-05
# A    1     2017-01-06
# B    1     2016-05-01
# B    0     2016-05-02
# B    1     2016-05-03
# B    0     2016-05-04
# B    1     2016-05-05