Message-ID: <971536df1001051122l58389037p4e16288aedfdeb07@mail.gmail.com>
Date: 2010-01-05T19:22:04Z
From: Gabor Grothendieck
Subject: mean for subset
In-Reply-To: <971536df1001051103h31db91b3h770dda8db9a20171@mail.gmail.com>
Here is the solution using sqldf which can do it in one statement:
> # read in data
> Lines <- "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"
>
> DF <- read.table(textConnection(Lines), header = TRUE)
>
> # run
> library(sqldf)
> sqldf("select NAME, avg(SCORE) from DF group by NAME having count(*) = 3")
NAME avg(SCORE)
1 James 64.00000
2 Tom 78.66667
On Tue, Jan 5, 2010 at 2:03 PM, Gabor Grothendieck
<ggrothendieck at gmail.com> wrote:
> 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]]
>>
>> ______________________________________________
>> R-help at 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.
>>
>