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

From: Charles C. Berry <cberry_at_tajo.ucsd.edu>
Date: Sun, 13 Jun 2010 13:56:06 -0700

On Sun, 13 Jun 2010, 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’.
>

If I understand you

         colSums( xtabs( ~ specie + unit , data ) !=0 )

HTH, Chuck

>> 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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>

Charles C. Berry                            (858) 534-2098
                                             Dept of Family/Preventive Medicine
E mailto:cberry_at_tajo.ucsd.edu	            UC San Diego
http://famprevmed.ucsd.edu/faculty/cberry/ La Jolla, San Diego 92093-0901



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