On 7/13/03 12:22 AM, "kjetil brinchmann halvorsen" <[EMAIL PROTECTED]> wrote:
> On 12 Jul 2003 at 18:50, Tor A Strand wrote: > > Hei! > >> Need to use generalized additive models and have therefore obtained R >> >> I am able to do the analysis but I have problems understanding the syntax >> and the options >> >> Can someone explain what some of the terms do in this model do:? >> >> c<-gam(depvar~var1+var2+s(var3)+s(var4, by=var5)+s(var6, var7)+s(var8,3), >> data=xdataset ) >> >> I do not use the terms including var4- var8 in my model, just want to know >> what they do. >> >> +s(var4, by=var5) > > Presumably var5 is a factor, separate smooths are calculated for each > level of the factor. This is a kind of interaction. > >> +s(var6, var7) > > This looks like a bivariate smooth, that is , a surface. Never tried > that. > >> +s(var8,3) > > second argument is the number of degrees of freedom. > >> >> Furthermore, the results become rather different when I change the model to: >> >> c<-gam(depvar~var1+var2-1+s(var3)+s(var4, by=var5)+s(var6, var7)+s(var8,3), >> data=xdataset ) >> # note just adding a -1 >> >> Why. > > This is removing the intercept from the model, and as all smooths are > centered at zero in some way, that should have more or less the same > effect as removing the intercept from a linear model. That can make a > HUGE difference. > >> >> Please forgive my ignorance. > > You probably have a local expert at Haukeland: Try to call > Tore Wenzel-Larsen if you need more help. > > Kjetil Halvorsen > All of the above were extremely useful. I will also ask Tore. Thanks ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help
