Message-ID: <OF933405E8.08627FC3-ONC1257589.0033EC0F-C1257589.00344226@precheza.cz>
Date: 2009-03-30T09:32:23Z
From: PIKAL Petr
Subject: Odp: How to generate a new column according to some rule?
In-Reply-To: <551b80f5-9409-48ef-87ac-b1d32d49d423@n7g2000prc.googlegroups.com>
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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