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

[David Winsemius]

On Sep 13, 2011, at 9:34 AM, Jean-Christophe BOUËTTÉ wrote:

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

I had a similar thought in that:  resA_B <- A - B  .... would give the  
"residuals" from a line through the origin with a slope of 1. No  
regression needed.

-- 
David


> ;-)
> 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.
>>>
>>> ______________________________________________
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>>> 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.
>>
>
> ______________________________________________
> 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.

David Winsemius, MD
West Hartford, CT