[R] extracting data from a dataframe

[A.J. Rossini]

>>>>> "tim" == Tim Wilson <wilson at visi.com> writes:

    tim> Hi everyone,
    tim> Here's a question about extracting data from a dataframe:

    tim> Let's say I've got a dataframe with two vectors, TEST and GENDER. GENDER
    tim> contains a 1 for males and 2 for females. I want to separate the results
    tim> of TEST by GENDER so I can compare their means.

    tim> What's the most efficient way to do this with R?

something like:

lapply(split(df$TEST,df$GENDER),mean)

?
(where "df" is the data.frame).

-- 
A.J. Rossini				Rsrch. Asst. Prof. of Biostatistics
U. of Washington Biostatistics		rossini at u.washington.edu	
FHCRC/SCHARP/HIV Vaccine Trials Net	rossini at scharp.org
-------------- http://software.biostat.washington.edu/ ----------------
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