In a data frame I have a column "date" and a column "time",now I want to generate a new column which is the mean of the value of time group by date. In stata the command is
egen scalls = mean(time),by(date) but I don't know the command in R, can anybody help me? ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
