[R] averaging within columns

[BXC (Bendix Carstensen)]

?tapply

Bendix Carstensen

> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch 
> [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of thomas hills
> Sent: Saturday, February 26, 2005 6:17 PM
> To: r-help at stat.math.ethz.ch
> Subject: [R] averaging within columns
> 
> 
> I have a dataframe with names in the first column and wait times 
> between decisions in the second column.  Since individuals make 
> multiple decisions, I want the average for each individual.  For 
> example, the data might look like this
> 
> name	wtime
> jo		1
> jo		2
> jo		1
> jo 		3
> tim		3	
> tim		2
> tim		2
> ro		1
> ro		2
> etc.
> 
> I'm hoping there is something like
> 
> mean(dataname$wtime[name])
> 
> which will just create a column with length equal to the number of 
> different names (levels) and an average wtime for each.  So 
> far though, 
> I haven't had much luck figuring that one out.
> 
> Thanks.
> Thomas
> 
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