[R] How to take the ave of two rows in a data frame

[John Kane]

Try the reshape package

This should do what you want.
================================================
library(reshape)
df1 <- melt(mydata, id=c("ID"),
measured=c("a1","a2","a3")) ; df1
stats  <- cast(df1, ID ~ variable  , mean) ; stats
=================================================


--- affy snp <affysnp at gmail.com> wrote:

> > Dear list,
> > I have a data frame like:
> >
> > > log2.ratios[1:3,1:4]
> >            ID                  a1             a2  
>           a3
> > 1 GS1-232B23      -0.0207500 0.17553833 
> 0.21939333
> > 2 RP11-82D16      -0.1896667 0.02645167
> -0.03112333
> > 3 RP11-62M23      -0.1761700 0.08214500
> -0.04877000
> > 4 RP11-62M23      0.2761700 -0.15214500
> -0.05877000
> >
> 
> the 3rd and 4th rows are of the same ID, I would
> like to take the avarage of
> these
> two rows and get the data frame to:
> 
>         ID                  a1             a2       
>      a3
> 1 GS1-232B23      -0.0207500 0.17553833  0.21939333
> 2 RP11-82D16      -0.1896667 0.02645167 -0.03112333
> 3 RP11-62M23      -0.05         -0.035          
> 0.094135
> 
> Can anyone suggest how to deal with this (to take
> the ave of two rows of the
> same ID ) more quickly?
> 
> Thanks a bunch!
> 
> Allen
> 
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> 
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