Message-ID: <971536df1001051103h31db91b3h770dda8db9a20171@mail.gmail.com>
Date: 2010-01-05T19:03:01Z
From: Gabor Grothendieck
Subject: mean for subset
In-Reply-To: <4b5c27441001051029l298e7438q5d31dc1b37a21b29@mail.gmail.com>
Have a look at this post and the rest of that thread:
https://stat.ethz.ch/pipermail/r-help/2010-January/223420.html
On Tue, Jan 5, 2010 at 1:29 PM, Geoffrey Smith <gps at asu.edu> wrote:
> Hello, does anyone know how to take the mean for a subset of observations?
> For example, suppose my data looks like this:
>
> OBS ? ? NAME ? SCORE
> 1 ? ? ? ? ?Tom ? ? ? 92
> 2 ? ? ? ? ?Tom ? ? ? 88
> 3 ? ? ? ? ?Tom ? ? ? 56
> 4 ? ? ? ? ?James ? ?85
> 5 ? ? ? ? ?James ? ?75
> 6 ? ? ? ? ?James ? ?32
> 7 ? ? ? ? ?Dawn ? ? 56
> 8 ? ? ? ? ?Dawn ? ? 91
> 9 ? ? ? ? ?Clara ? ? 95
> 10 ? ? ? ?Clara ? ? 84
>
> Is there a way to get the mean of the SCORE variable by NAME but only when
> the number of observations is equal to 3? ?In other words, is there a way to
> get the mean of the SCORE variable for Tom and James, but not for Dawn and
> Clara? ?Thank you.
>
> --
> Geoffrey Smith
> Visiting Assistant Professor
> Department of Finance
> W. P. Carey School of Business
> Arizona State University
>
> ? ? ? ?[[alternative HTML version deleted]]
>
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