[R] Force regression line to a 1:1 relationship

[John Fox]

Dear JC,

> -----Original Message-----
> From: Jean-Christophe BOUËTTÉ [mailto:jcbouette at gmail.com]
> Sent: September-13-11 9:35 AM
> To: John Fox
> Cc: RCulloch; r-help at r-project.org
> Subject: Re: [R] Force regression line to a 1:1 relationship
> 
> And you can easily get these predictions using the following code :
> A <- B

Indeed, which is why it's not clear to me that the model object is of real
use. I suppose that it could be used for AIC(), anova(), etc.

Best,
 John

> 
> ;-)
> JC
> 
> 2011/9/13 John Fox <jfox at mcmaster.ca>:
> > Dear Ross,
> >
> > lm(y ~ 0 + offset(x)) will do the trick, but the resulting model has
> > no coefficient estimates and thus can't be used with abline(). You
> > can, e.g., get predictions from the model, but I'm not sure what real
> > use it will be to you.
> >
> > I hope this helps,
> >  John
> >
> > --------------------------------
> > John Fox
> > Senator William McMaster
> >  Professor of Social Statistics
> > Department of Sociology
> > McMaster University
> > Hamilton, Ontario, Canada
> > http://socserv.mcmaster.ca/jfox
> >
> >
> >
> >> -----Original Message-----
> >> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> >> project.org] On Behalf Of RCulloch
> >> Sent: September-13-11 7:03 AM
> >> To: r-help at r-project.org
> >> Subject: [R] Force regression line to a 1:1 relationship
> >>
> >> Hello,
> >>
> >> I appreciate this is likely to be an easy question. I am trying to
> >> obtain the residuals from a linear regression where the line is
> >> forced to have a
> >> 1:1 relationship.
> >>
> >> An example of the data:
> >>
> >> A<-c(0.9803922, 1.3850416, 0.8241758, 0.0000000, 0.4672897,
> >> 1.1904762, 0.0000000, 0.9456265,
> >> 1.5151515)
> >> B<-c(1.3229572, 1.9471488, 1.3182674, 0.7007708, 1.0185740,
> >> 1.0268562, 0.8695652, 0.3016591, 1.9667171)
> >>
> >> plot(A, B, ylim=c(0,2), xlim=c(0,2))
> >> abline(0,1, col="lightgrey", lty="dashed",lwd=2)#1:1 relationship =
> >> what I want to use in the lm()
> >>
> >> #Normal regression
> >> AB<-lm(A~B)
> >>
> >> #plot regression line
> >> abline(lm(AB))
> >>
> >>
> >> How can I force the regression to have a 1:1 relationship, I assume
> >> it is to do with offset() but I have somewhat fried my brain trying
> >> numerous variations and I am not convinced any are correct. I was
> >> also hoping the plot function would show me that the calculation is
> >> correct, but any time I use the offset() command there is no line
> plotted?
> >>
> >> Any hints or tips would be much appreciated!
> >>
> >> Ross
> >>
> >>
> >>
> >> --
> >> View this message in context: http://r.789695.n4.nabble.com/Force-
> >> regression-line-to-a-1-1-relationship-tp3809733p3809733.html
> >> Sent from the R help mailing list archive at Nabble.com.
> >>
> >> ______________________________________________
> >> R-help at 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.
> >
> > ______________________________________________
> > R-help at 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.
> >