[R] Newbie: how to calculate group averagege?

[Peter Dalgaard BSA]

Sven Garbade <garbade at psy.uni-muenchen.de> writes:

> For each combinations of the factors are 6 values of rt. I need the mean
> of the six rt values for each factor combination. I´ve tried the ave()
> function:
> 
> > ave(rt, zf, xf, yf)
> 
> but it returns a lot of NAs. Is there another r-function I´ve overlooked
> or must I write my own function?

I think you're looking for

tapply(rt,list(zf, xf, yf), mean, na.rm=T)

alternatively, 

ave(rt, zf, xf, yf, FUN=function(x)mean(x,na.rm=T)) 

-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907
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