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

Jean-Christophe BOUËTTÉ jcbouette at gmail.com
Tue Sep 13 15:34:31 CEST 2011

And you can easily get these predictions using the following code :
A <- B

;-)
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
> 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.
>>
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