Odp: How to generate a new column according to some rule?
Hi r-help-bounces at r-project.org napsal dne 30.03.2009 05:17:35:
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?
In R you can use ?tapply ?by ?aggregate from base or functions from ?doBy package. Regards Petr
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