[R] Error in plot.lm

[Peter Ehlers]

On 2011-03-11 11:31, David Winsemius wrote:
> On Mar 11, 2011, at 2:06 PM, Jeff Newmiller wrote:
>
>> >  I am encountering an error with plot.lm:
>> >
>>> >>  tstdf<- data.frame( y=c(1.01,1.98,3.02,3.99),x=c(1,2,3,4))
>>> >>  plot(lm(I(y) ~ x, data=tstdf))
>> >  Hit<Return>  to see next plot:
>> >  Hit<Return>  to see next plot:
>> >  Error in object$coefficients : $ operator is invalid for atomic
>> >  vectors
>> >
>> >  Obviously I don't need the I() in this example, but I have been
>> >  working
>> >  with regressions that involve an expression on the left side of the
>> >  formula, for which I do need the I().
> Are you sure you need I() on the LHS? The I function is designed to
> avoid the confusion related to the  dual use of the arithmetic
> operator symbols affecting the construction of the model matrix, but I
> don't think that applies to the LHS of the formula.
>
> (See Dalgaard's commentshttp://finzi.psych.upenn.edu/Rhelp10/2009-March/192018.html
>    if desiring higher authority.)

Agreed that I() is not needed.
For anyone interested in why the (non)problem arises:
the residuals component of the model will have a class
attribute ("AsIs") which causes abline() (called by
qqline()) to choke.

Peter Ehlers

>
> -- David.
>> >  I can work around by declaring a new actual column with the computed
>> >  result, but this seems otherwise unnecessary.
>> >
>> >  Is this behaviour intended?
>> >
>>> >>  R.Version()
>> >  $platform
>> >  [1] "i386-pc-mingw32"
>> >
>> >  $arch
>> >  [1] "i386"
>> >
>> >  $os
>> >  [1] "mingw32"
>> >
>> >  $system
>> >  [1] "i386, mingw32"
>> >
>> >  $status
>> >  [1] ""
>> >
>> >  $major
>> >  [1] "2"
>> >
>> >  $minor
>> >  [1] "12.1"
>> >
>> >  $year
>> >  [1] "2010"
>> >
>> >  $month
>> >  [1] "12"
>> >
>> >  $day
>> >  [1] "16"
>> >
>> >  $`svn rev`
>> >  [1] "53855"
>> >
>> >  $language
>> >  [1] "R"
>> >
>> >  $version.string
>> >  [1] "R version 2.12.1 (2010-12-16)"
>> >
>> >
>> >  ---------------------------------------------------------------------------
>> >  Jeff Newmiller                        The     .....       .....  Go
>> >  Live...
>> >  DCN:<jdnewmil at dcn.davis.ca.us>         Basics: ##.#.       ##.#.
>> >  Live Go...
>> >                                        Live:   OO#.. Dead: OO#..
>> >  Playing
>> >  Research Engineer (Solar/Batteries            O.O#.       #.O#.  with
>> >  /Software/Embedded Controllers)               .OO#.       .OO#.
>> >  rocks...1k
>> >
>> >  ______________________________________________
>> >  R-help at r-project.org  mailing list
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>> >  PLEASE do read the posting guidehttp://www.R-project.org/posting-guide.html
>> >  and provide commented, minimal, self-contained, reproducible code.
> David Winsemius, MD
> West Hartford, CT
>
> ______________________________________________
> R-help at r-project.org  mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guidehttp://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.