[R] presence/absence matrix

[Stefano Calza]

What about

table(sample,species)

Stefano


On Fri, Jul 20, 2007 at 04:16:39PM +0200, rocchini a unisi.it wrote:
<rocchini>I have a table such that:
<rocchini>
<rocchini>sample #   species
<rocchini>1    a
<rocchini>1    b
<rocchini>2    a   
<rocchini>2    c
<rocchini>3    b     
<rocchini>
<rocchini>and i would like to build a matrix with species names (i.e. a b and c) 
<rocchini>as field names and samples (i.e. 1,2 and 3) as row names
<rocchini>and 1/0 as inner values
<rocchini>such as:
<rocchini>    a   b   c
<rocchini>1   1   1   0
<rocchini>2   1   0   1
<rocchini>3   0   1   0
<rocchini>
<rocchini>I am currently using Rcmdr package for managing datasets but need a 
<rocchini>function about.... I tried to use stack function but only with worst results
<rocchini>
<rocchini>Thanks
<rocchini>Duccio
<rocchini>
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