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

[Christos Hatzis]

Take a look at ?reshape - it is used to convert between 'long' and 'wide'
formats of data tables (frames). 

-Christos 

> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On Behalf Of 
> Billy_Schweiger at nps.gov
> Sent: Friday, January 25, 2008 4:30 PM
> To: r-help at r-project.org
> Subject: [R] Function for translation of a list into a matrix 
> as used byordination?
> 
> 
> 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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