Dear All, I've a question about scaling the input variables for an analysis with svm (package e1071). Most of my variables are factors with 4 to 6 levels but there are also some numeric variables. I'm not familiar with the math behind svms, so my assumtions maybe completely wrong ... or obvious. Will the svm automatically expand the factors into a binary matrix? If I add numeric variables outside the range of 0 to 1 do I have to scale them to have 0 to 1 range? thanks a lot for help, +kind regards, Arne
Arne.Muller at sanofi-aventis.com wrote:> Dear All, > > I've a question about scaling the input variables for an analysis with svm (package e1071). Most of my variables are factors with 4 to 6 levels but there are also some numeric variables. > > I'm not familiar with the math behind svms, so my assumtions maybe completely wrong ... or obvious. Will the svm automatically expand the factors into a binary matrix? If I add numeric variables outside the range of 0 to 1 do I have to scale them to have 0 to 1 range?Well, this depends on the kernel in use. For radial basis functions (as an example), you do not have to rescale, but a transformation of variables might make sense in order to get better results, though. Uwe Ligges> > thanks a lot for help, > > +kind regards, > > Arne > > ______________________________________________ > R-help at 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
Arne.Muller at sanofi-aventis.com wrote:> Dear All, > > I've a question about scaling the input variables for an analysis with > svm (package e1071). Most of my variables are factors with 4 to 6 > levels but there are also some numeric variables. > > I'm not familiar with the math behind svms, so my assumtions maybe > completely wrong ... or obvious. Will the svm automatically expand the > factors into a binary matrix?yes.> If I add numeric variables outside the range of 0 to 1 do I have to > scale them to have 0 to 1 range?svm() will scale your data by default. Cheers, David -- Dr. David Meyer Department of Information Systems and Operations Vienna University of Economics and Business Administration Augasse 2-6, A-1090 Wien, Austria, Europe Fax: +43-1-313 36x746 Tel: +43-1-313 36x4393 HP: http://wi.wu-wien.ac.at/~meyer/