> -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Thomas Lumley > Sent: Wednesday, April 07, 2004 5:44 PM > To: Giovanni Petris
> On Wed, 7 Apr 2004, Giovanni Petris wrote: > > > > > Hello, > > > > After reading the help for predict.lm and predict.glm, it > is not clear > > to me what are the values returned by predict( ..., type="terms"). > > > > Anybody willing to enlighten me? > > > > For each term in the formula, extract its coefficients and > the corresponding columns of the design matrix, and multiply > the two, and then center the result. > > So, looking at the example in example(termplot) we have a > model y~ns(x,6)+z where z is a factor with 4 levels. > > There are 9 coefficients in the model, but only two terms: > ns(x,6) (based on 5 coefficients) and z (based on 3 coefficients). > > Adding up the terms and the centering value (also returned by > predict(,type="terms")) gives the linear predictor. 1) It would be useful to have this in the help file for predict.(g)lm Also that the constant is accessed as attr( pr.obj, "const" ) 2) A link to termplot might be useful too. 3) I guess that Giovanni (as well as I) was curious what the rationale behind the centering of effects is. Can anyone tell us? Bendix Carstensen ---------------------- Bendix Carstensen Senior Statistician Steno Diabetes Center Niels Steensens Vej 2 DK-2820 Gentofte Denmark tel: +45 44 43 87 38 mob: +45 30 75 87 38 fax: +45 44 43 07 06 [EMAIL PROTECTED] www.biostat.ku.dk/~bxc ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
