Hi,

you could try the reshape package,

l = list(d1= data.frame(ID=letters[1:4],value=1:4),
          d2= data.frame(ID=letters[1:4],value= -c(1:4)))

library(reshape)
m = melt(l)

cast(m, .~ID, fun=mean)

HTH,

baptiste

2009/7/15 Mark Na <mtb954@gmail.com>

> Dear R-helpers,
> I have a list containing 5000 elements, each element is a dataframe
> containing one ID column (identical over the 5000 dataframes) and 9 numeric
> variables, e.g.
>
> ID VAR1 VAR2 VAR3 ... VAR9
>
> I would like to create a new dataframe containing the ID column and the
> mean
> values of the 9 numeric variables. So, the structure of this new dataframe
> would be identical to the structure of the dataframes stored in my list
> (and
> the ID column would also be identical) but the values would be mean values.
>
> I've been attempting to do this with rowMeans and subscripting the list
> using double square brackets, but I can't get it to work.
>
> I'd appreciate any pointers to get me going, thanks!
>
> Mark Na
>
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>
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> PLEASE do read the posting guide
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> and provide commented, minimal, self-contained, reproducible code.
>



-- 

_____________________________

Baptiste Auguié

School of Physics
University of Exeter
Stocker Road,
Exeter, Devon,
EX4 4QL, UK

Phone: +44 1392 264187

http://newton.ex.ac.uk/research/emag
______________________________

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