On 23-Aug-07 09:56:33, Michal Kneifl wrote: > Please could anyone help me? > How can I fit a linear model where an intercept has no sense? > Thanks in advance.. > > Michael
Presumably you mean "where a non-zero intercept has no sense"? Suppose the model you want to fit is like Response ~ B+C+X+Y Then [A] lm(Response ~ B+C+X+Y) will give you an intecept. But: [B] lm(Response ~ B+C+X+Y - 1 ) will in effect force a zero intercept -- it removes the "Intercept" term (which is implicit in the form [A]) from the model, thus in effect giving it coefficient zero. In "real life", the model at [A] corresponds to the equation Response = a*1 + b*B + c*C + x*X + y*Y + error where a,b,c,x,y are the coefficients, so the "terms in the model" are 1 , B , C , X , Y. The model at [B] corresponds to Response = b*B + c*C + x*X + y*Y + error so the "terms in the model" are B , C , X , Y -- i.e. the same as before but with the term "1" removed, which is what is effected by adding the term "-1" to the model formula. Hoping this helps, Ted. -------------------------------------------------------------------- E-Mail: (Ted Harding) <[EMAIL PROTECTED]> Fax-to-email: +44 (0)870 094 0861 Date: 23-Aug-07 Time: 12:21:24 ------------------------------ XFMail ------------------------------ ______________________________________________ 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 and provide commented, minimal, self-contained, reproducible code.
