[R] presence/absence matrix

[Francisco J. Zagmutt]

See ?table  i.e.

 > x
   sample # species
1        1       a
2        1       b
3        2       a
4        2       c
5        3       b

 > table(x)
         species
sample # a b c
        1 1 1 0
        2 1 0 1
        3 0 1 0

Regards,

Francisco

Francisco J. Zagmutt


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