[R] dataframes and factors

[Wolfgang Koller]

Dear R-List,

I have a dataframe X containing factor f and numeric variable x1, x2, ... I
want to create a new dataframe (or possibly a matrix) that gives statistics
(e.g. sum) for the variables x1, x2, ... in each group defined by factor f.
What is the simplest way to do this?

I tried:
  attach(X)
  Z <- data.frame(f=levels(f),x1=as.vector(lapply(split(x1,f),sum)))

and stumbled on:
  Error in data.frame(f = levels(f), x1 = as.vector(lapply(split(x1, f),  : 
        arguments imply differing number of rows: 5, 1

Help is much appreciated,

Wolfgang Koller


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Wolfgang Koller,  koller2 at fgr.wu-wien.ac.at
Forschungsinstitut für Europafragen
Wirtschaftsuniversitaet Wien
Althanstrasse 39-45, 1090 Vienna, Austria
http://fgr.wu-wien.ac.at/institut/ef/ief-home.htm
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