[R] Calculate Mean for each Treatment/Trial Interaction in DF

[Peter Alspach]

Tena koe Jim

?aggregate

HTH ....

Peter Alspach
 

> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On Behalf Of jimdare
> Sent: Friday, 6 November 2009 2:54 p.m.
> To: r-help at r-project.org
> Subject: [R] Calculate Mean for each Treatment/Trial Interaction in DF
> 
> 
> Hi,
> 
> I am create a new DF that summarizes the mean angle per 
> treatment/trial, of the original DF (see below).  I have had 
> some success using:
> (tapply(df$Angle, INDEX=interaction(df$State, df$Trial),  
> FUN=mean)); however, this gives the answer as a list, which 
> means I would have to split the name to get the categories back.  Does
> anyone know a simple way to transform the Original DF into 
> Summary DF?    
> 
> Thanks in advance,
> 
> James
> 
> 
> Original DF
> 
> > df
>        Angle Trial    Treatment
> 1    43.1297     1   C
> 2    62.3613     1   C
> 3    88.2767     2   C
> 4    75.2431     2   C
> 5    91.3668     3   C
> 6    61.2800     3   C
> 7    55.5575     1   U
> 8    69.4661     1   U
> 9    67.5512     2   U
> 10   95.5528     2   U
> 11   75.8689     3   U
> 12   66.9070     3   U
> 
> Summary DF
> 
> > sdf
> 
>        Angle Trial    Treatment
> 1    52.7455   1   C
> 2    ...           2   C
> 3    ...           3   C
> 4    ...           1   U
> 5    ...           2   U
> 6    ...           3   U
> 
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