R help - Feb 2015 - Averaging column scores when participants vary in number of observations

And just to muddy the waters more here's another way to do it using the
handy plyr package where the data.frame is "dat1"

library(plyr)
ddply(dat1, .(Participant.ID), summarize, mean = mean(Score))

John Kane
Kingston ON Canada

> -----Original Message-----
> From: js.huang at protective.com
> Sent: Thu, 19 Feb 2015 17:36:19 -0800 (PST)
> To: r-help at r-project.org
> Subject: Re: [R] Averaging column scores when participants vary in number
> of observations
> 
> Hi,
> 
>   Another implication:
> 
>> data1
>   Observation Participant.ID Video.Coder Score
> 1           A              1      Donald     4
> 2           B              1       Tracy     5
> 3           C              2      Donald     6
> 4           D              3         Sam     2
> 5           E              3       Tracy     3
> 6           F              4      Donald     2
> 7           G              4       Tracy     1
> 8           H              5         Sam     8
>> tapply(data1$Score,data1$Participant.ID,mean)
>   1   2   3   4   5
> 4.5 6.0 2.5 1.5 8.0
> 
> 
> 
> 
> --
> View this message in context:
>
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> Sent from the R help mailing list archive at Nabble.com.
> 
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