[R] Function for translation of a list into a matrix as used by ordination?

[Henrique Dallazuanna]

Try this also:

 noquote(tapply(x$Abundance, list(x$Plot, x$Species), paste))

On 25/01/2008, Billy_Schweiger at nps.gov <Billy_Schweiger at nps.gov> wrote:
>
> Hello.
>
> Does anyone know of an existing function that takes a list in the form of:
>
> Plot1 Species1    Abundance1
> Plot1 Species2    Abundance2
> Plot2 Species1    Abundance1
> Plot2 Species3    Abundance3
> .
> .
> .
> PlotN SpeciesN    AbundanceN
>
> and translates into a matrix in the form of
>
>       Species1    Species2....      SpeciesN
> Plot1 Abundance1  Abundance2...     AbundanceN
> Plot2 Abundance1  Abundance2...     AbundanceN
> .
> .
>
> .
> PlotN AbundanceN  AbundanceN...     AbundanceN
>
>
> This is a basic operation used in the initial stages of ordination etc of
> ecological data (vegetation or other species) that is usually stored in a
> database or flatfile in the list format above. It is similar to a cross
> tabulation like the function xtabs(), however its useful to be able to
> control whether a measured abundance for a taxa is included or a boolean
> (presence/absence) for the taxa in a given plot.
>
> Im new to such analyses in R, but before writing it myself hope or suspect
> that such a function or library is out there (although I dont see it after
> some quick searching in things like Vegan or BiodivesityR or labdsv).
>
>
> Thanks
> billy
>
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>


-- 
Henrique Dallazuanna
Curitiba-Paraná-Brasil
25° 25' 40" S 49° 16' 22" O