Hi, a first step to answer your question: Regression through the origin (= without intercept) can be done by explicitly stating in the 'formula' argument '-1' If you check the help page of 'lm' for example:
help(lm) It will say in the 'Details' section: A formula has an implied intercept term. To remove this use either 'y ~ x - 1' or 'y ~ 0 + x'. See 'formula' for more details of allowed formulae. An example is given at the end of the help page: ## Annette Dobson (1990) "An Introduction to Generalized Linear Models". ## Page 9: Plant Weight Data. ctl <- c(4.17,5.58,5.18,6.11,4.50,4.61,5.17,4.53,5.33,5.14) trt <- c(4.81,4.17,4.41,3.59,5.87,3.83,6.03,4.89,4.32,4.69) group <- gl(2,10,20, labels=c("Ctl","Trt")) weight <- c(ctl, trt) anova(lm.D9 <- lm(weight ~ group)) summary(lm.D90 <- lm(weight ~ group - 1))# omitting intercept I hope this helps a bit. Best, Roland > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Trujillo L. > Sent: Tuesday, May 23, 2006 12:54 PM > To: r-help@stat.math.ethz.ch > Subject: [R] Regression through the origin > > Dear R-users: > > Sorry for the naiveness of my question but I have been trying in the > R-help and the CRAN website without any success. I am trying > to perform > a regression through the origin (without intercept) and my > main concern > is about its evaluative statistics. It is clear for me that R squared > does not make sense if you do not have an intercept in your model and > how big is the assumption that the response is zero when all the > predictors are zero. If I still want to perform a regression in that > conditions, does R have any options to evaluate the model adequacy > correctly? > > Thanks in advance, > > Leonardo Trujillo. > > ______________________________________________ > 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 > ---------- This mail has been sent through the MPI for Demographic Rese...{{dropped}} ______________________________________________ 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