[R] Count of unique factors within another factor

From: Birdnerd <haaszoology_at_gmail.com>
Date: Sun, 13 Jun 2010 09:07:06 -0700 (PDT)

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--

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Received on Sun 13 Jun 2010 - 18:07:29 GMT

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