[R] update?

[Gabor Grothendieck]

Actually I tried it and a version of nonadd which
corresponds to my prior solution can be written
without using external packages in only 2
extra lines:

nonadd <- function(formula.) {
	f <- lm(formula.)
	e <- new.env(parent = environment(formula.))
	e$v <- f$fitted.values^2
	g <- update(f, . ~ . + v, data = e)
	anova(f, g)
}
x <- rnorm(20)
y <- rnorm(20)
nonadd(y ~ x)


On 1/2/06, Gabor Grothendieck <ggrothendieck at gmail.com> wrote:
> Here is another solution in addition to the ones already
> provided.   This creates a proto object which is an
> environment that contains v and whose parent is
> the formula's environment.  update will look in the proto
> object and find v.  It won't find x and y but will next
> look to the parent of the proto object and will find them there.
> The proto package makes it convenient to create an environment
> with a specified parent and contents all in one line
> but at the expensive of a few more lines you could also do
> it without the proto package.
>
> library(proto)
> nonadd <- function(formula.) {
>   f <- lm(formula.)
>   g <- update(f, . ~ . + v, data = proto(environment(formula.), v =
> f$fitted.values^2))
>   anova(f, g)
> }
>
> x <- rnorm(20)
> y <- rnorm(20)
> nonadd(y ~ x)
>
>
>
> On 1/2/06, roger koenker <rkoenker at uiuc.edu> wrote:
> > I'm having problems with environments and update() that
> > I expect have a simple explanation.  To illustrate, suppose
> > I wanted to make a very primitive Tukey one-degree-of-
> > freedom for nonadditivity test and naively wrote:
> >
> > nonadd <- function(formula){
> >         f <- lm(formula)
> >         v <- f$fitted.values^2
> >         g <- update(f, . ~ . + v)
> >         anova(f,g)
> >         }
> >
> > x <- rnorm(20)
> > y <- rnorm(20)
> > nonadd(y ~ x)
> >
> > Evidently, update is looking in the environment producingf f and
> > doesn't find v, so I get:
> >
> > Error in eval(expr, envir, enclos) : Object "v" not found
> >
> > This may (or may not) be related to the discussion at:
> > http://bugs.r-project.org/cgi-bin/R/Models?id=1861;user=guest
> >
> > but in any case I hope that someone can suggest how such
> > difficulties can be circumvented.
> >
> >
> > url:    www.econ.uiuc.edu/~roger            Roger Koenker
> > email    rkoenker at uiuc.edu            Department of Economics
> > vox:     217-333-4558                University of Illinois
> > fax:       217-244-6678                Champaign, IL 61820
> >
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>