
Thank you very much for your kind reply, I have found that the error was in the stdCoeff function and not in the linear model. summary() works pretty well on my model, I will simply use another function to compute my coefficients.
Best regards,
Jennifer

> Date: Wed, 4 Aug 2010 15:27:40 -0500
> From: eriki@ccbr.umn.edu
> To: jennifer.hou@hotmail.de
> CC: r-help@r-project.org
> Subject: Re: [R] regression analysis with interactions
> 
> 
> 
> Jennifer Hou wrote:
> > Hello,
> > 
> > I have got a linear model that looks like this:
> > lm(criterion ~ variable.A*variable.a + variable.B*variable.b + variable.C *variable.c)
> > 
> > The output computed with stdCoeff() seems to be all right, but it does not show the coefficients of the interaction of the first pair of variables. Instead, it shows "NA":
> > 
> 
> And what package is the `stdCoeff` function in? If we don't have a 
> reproducible example, it's very hard to help.
> 
> What does calling the summary function on your lm object give you?
> 
> 
> > (Intercept) 
> > NA 
> >                                                       
> > variable.A
> >  0.0925094150 
> > variable.a
> > 0.1517246479 
> > variable.B
> > -0.0023847092 
> > variable.b
> > 0.0256653197 
> > variable.C
> > 0.0194313471 
> > variable.c
> > 0.0192897539 
> > 
> > variable.A : variable.a
> > NA 
> > variable.B : variable.b
> > 0.0471111439 
> > variable.C : variable.c
> > 0.0696702457 
> > ______________________________________________
> > R-help@r-project.org 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.
 		 	   		  
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