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

David Winsemius dwinsemius at comcast.net
Tue Sep 13 17:56:40 CEST 2011

On Sep 13, 2011, at 11:44 AM, David Winsemius wrote:

> On Sep 13, 2011, at 9:43 AM, RCulloch wrote:
>> Dear John,
>> Thank you for that, and for explaining why the abline() command  
>> wont/dosen't
>> work. The approach is based on reviewers comments that I am a tad  
>> sceptical
>> about myself but yet curious enough to test their suggestion......I  
>> don't
>> think it is very straightforward to explain; however, it involves  
>> using the
>> residuals of the lm() and plotting them against a covariate to assess
>> whether or not the deviation from the 1:1 relationship is in someway
>> influenced by the other covariate. I hope that shines a small  
>> amount of
>> light on this rather unorthodox approach?!
> Plotting the residuals against a covariate is a standard way to  
> assess the assumption that the residuals are distributed normally  
> around each continuous regressor and have no non-linear relationship  
> around each continuous regressor
Forgot to include homoschedasticity:

   ...and have a reasonably constant standard deviation across the  
range of the regressor...

> . It is not to assess a "1:1 relationship", whatever that is. I  
> think we would need to  see a complete quotation of the reviewer's  
> comments before deciding who is confused in this interchange.
> -- 
> David Winsemius, MD
> West Hartford, CT
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David Winsemius, MD
West Hartford, CT

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