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 comments http://finzi.psych.upenn.edu/Rhelp10/2009-March/192018.html
if desiring higher authority.)
--
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)"
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