[R] average by group...

[Doran, Harold]

?tapply
 

> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch 
> [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of r user
> Sent: Tuesday, May 30, 2006 12:27 PM
> To: rhelp
> Subject: [R] average by group...
> 
> I have a dataframe with 700,000 rows and 2 vectors
> (columns): "group" and "score".
> 
> I  wish to calculate a third vector of length 700000:
> the average score by group.  Even though the avarge value 
> will repeat, I wish to return the average for that particular 
> group for each row.
> 
> (I know I can do this by calculating each group's average and 
> then using the merge command, but as my calculations get more 
> complex and my data set gets larger, the merge command seems 
> to be fairly slow.)
> 
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