One thing to etch into your brain: Don't use constructs like lm(p1$y~p1$x1+p1$x2)
Instead, use: lm(y ~ x1 + x2, data=p1) Doing the former is only asking for trouble when it comes time to do prediction. It will look for `p1$y' in the newdata, and of course, won't find it there! Andy > From: Anne > > Hi all, > > I still have problems with the predict function by setting up > the values on > which I want to predict > > ie: > original df: p1 (193 obs) variates y x1 x2 > > rm(list=ls()) > x1<-rnorm(193) > x2<-runif(193,-5,5) > y<-rnorm(193)+x1+x2 > p1<-as.data.frame(cbind(y,x1,x2)) > p1 > y x1 x2 > 1 -0.6056448 -0.1113607 -0.5859728 > 2 -4.2841793 -1.0432688 -3.3116807 > ...... > 192 -1.3228239 1.0263013 -2.7801324 > 193 1.8736683 1.0480632 0.4746959 > > newdf<-data.frame(x1= seq(min( p1$x1),max( p1$x1),length=10), > x2=rep(median( p1$x2),10) ) > pr<-predict(g<-lm(p1$y~p1$x1+p1$x2) ,newdf, se.fit = TRUE) > > newdf > x1 x2 > 1 -2.3844149 -0.2594991 > 2 -1.8388635 -0.2594991 > ... > 9 1.9799963 -0.2594991 > 10 2.5255477 -0.2594991 > > pr$fit > 1 -0.6766906 > 2 -4.4198864 > ..... > 192 -1.6531906 > 193 1.6395442 > > so apparently the predict() function did not take up the new > data.frame > > > I looked up with conflicts() to see if I had masked objects > in the search > path potentially causing this problem > but found none > > > > Thanks and a good week end! (I for one need it) > Anne > ---------------------------------------------------- > Anne Piotet > Tel: +41 79 359 83 32 (mobile) > Email: [EMAIL PROTECTED] > --------------------------------------------------- > M-TD Modelling and Technology Development > PSE-C > CH-1015 Lausanne > Switzerland > Tel: +41 21 693 83 98 > Fax: +41 21 646 41 33 > > ______________________________________________ > [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 > > ______________________________________________ [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
