[R] table function
P.Dalgaard at biostat.ku.dk
Mon Jul 16 12:03:13 CEST 2007
sigalit mangut-leiba wrote:
> Hello all,
> I want to use the "table" function, but for every id I have a different no.
> of rows (obs.).
> If I write:
> table(x$class, x$infec)
> I don't get the right frequencies because I should count every id once, if
> id 1 has 20 observations It should count as one.
> can I use unique func. here?
> Hope it's clear.
Almost. I assume that class and infect are constant over id? (If people
change infection status during the trial, you have a more complex problem).
You could then use unique() like this
with(unique(x[c("id", "class", "infec")] , table(class, infec)),
but I'd prefer using duplicated() as in
with(subset(x, !duplicated(id)), table(class, infec))
(notice that the latter tabulates the first record for each id, whereas
the former will count ids multiple times if the change class or infec).
O__ ---- Peter Dalgaard Øster Farimagsgade 5, Entr.B
c/ /'_ --- Dept. of Biostatistics PO Box 2099, 1014 Cph. K
(*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk) FAX: (+45) 35327907
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