On Friday 23 September 2005 17:08, Dave Roberts wrote: > Martin, > > If the data are actually coded 0/1, the tree function would > probably intepret them as integers and try a regression instead of a > classification. If the dependent variable is called "var", try
thanks, but I think I provided too less informations. My dependent variable are the locations which are names (I could transform them to numbers from 1 - n). The independent variables consist of 0/1 data (species). If I do tree(locations~factor(species1)+factor(species2)+.....+factor(speciesn), sp_data) I receive the same results as without the factor() part. BTW just a subset of the locations are displayed what is pretty weird considering that I included all locations in the analysis. Martin > x <- tree(factor(var)~species) > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > David W. Roberts office 406-994-4548 > Professor and Head FAX 406-994-3190 > Department of Ecology email [EMAIL PROTECTED] > Montana State University > Bozeman, MT 59717-3460 > > Martin Wegmann wrote: > > Dear R-user, > > > > I tried to generate classification / regression tree with a > > absence/presence matrix of species (400) in different locations (50) to > > visualise species which are important for splitting up two locations. > > Rpart and tree did not work for more than 10 species which is logical due > > to the limited amount of locations (n=50). However the error prompt is a > > "+" and no specific message, but I am pretty sure that I did not enter a > > false sign by mistake. > > Is it allowed at all to use 0/1 data for this statistical technique and > > if yes is there a way or different method to use all 400 species entries? > > Otherwise I would apply a PCA beforehand but I would prefer to have the > > raw species informations. > > > > using R 2.1.1-1 (debian repos.) > > > > regards, Martin > > ______________________________________________ > R-help@stat.math.ethz.ch mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide! > http://www.R-project.org/posting-guide.html -- Martin Wegmann DLR - German Aerospace Center German Remote Sensing Data Center @ Dept.of Geography Remote Sensing and Biodiversity Unit && Dept. of Animal Ecology and Tropical Biology University of Wuerzburg Am Hubland 97074 Würzburg phone: +49-(0)931 - 888 4797 mobile: +49-(0)175 2091725 fax: +49-(0)931 - 888 4961 http://www.biota-africa.org http://www.biogis.de ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html