Take a look at ?reshape - it is used to convert between 'long' and 'wide' formats of data tables (frames).
-Christos > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of > [EMAIL PROTECTED] > Sent: Friday, January 25, 2008 4:30 PM > To: r-help@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 > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > > ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
