Question

We have retailer data stored in a database, if there is no sale for one item, then there is no row for that item in the database. So after fetch the data from database to R, there will be same gap in the result time series. Is there any way the remove the time series in R (insert back the missing data with value of 0)?

Answer 1

As shown only yesterday, just construct a vector with the desired timeframe, and merge.

# Your dataframe
DF <- data.frame(day = seq(as.POSIXlt("2011-01-17"),
                           as.POSIXlt("2011-02-14"),
                           by = "days")[seq(1, 30, by = 4)][-6],
                 value = c(5,5,7,8,4,6,5,6,9,8,6,6,4,6))

# new dataframe
full <- data.frame(day = seq(min(DF$day),max(DF$day),by = "days"),
                   value = 0)
# the big merge trick                   
merge(DF,full,all=T)

See also this question from yesterday.