Re: [R] Count of unique factors within another factor

From: Jorge Ivan Velez <jorgeivanvelez_at_gmail.com>
Date: Sun, 13 Jun 2010 14:12:14 -0400

Hi there,

Try

with(data, tapply(species, unit, function(x) length(unique(x))))

HTH,
Jorge

On Sun, Jun 13, 2010 at 12:07 PM, Birdnerd <> wrote:

>
> I have a data frame with two factors (sampling 'unit', 'species'). I want
> to
> calculate the number of unique 'species' per 'unit.' I can calculate the
> number of unique values for each variable separately, but can't get a count
> for each ‘unit’.
>
> > data=read.csv("C:/Desktop/sr_sort_practice.csv")
> > attach(data)
>
> > data[1:10,]
> unit species
> 1 123 ACMA
> 2 123 LIDE
> 3 123 LIDE
> 4 123 SESE
> 5 123 SESE
> 6 123 SESE
> 7 345 HEAR
> 8 345 LOHI
> 9 345 QUAG
> 10 345 TODI…..
>
> > sr.unique<- lapply (data, unique)
> $unit
> [1] 123 345 216
> $species
> [1] ACMA LIDE SESE HEAR LOHI QUAG TODI UMCA ARSP LIDE
>
> > sapply (sr.unique,length)
> unit species
> 3 10
>
> Then, I get stuck here because this unique species count is not given for
> each ‘unit’.
> What I'd like to get is:
>
> unit species
> 123 3
> 345 4
> 216 --
>
> Thanks--
>
> --
> View this message in context:
> http://r.789695.n4.nabble.com/Count-of-unique-factors-within-another-factor-tp2253545p2253545.html
> Sent from the R help mailing list archive at Nabble.com.
>
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