Why are you using expand.model.frame to update a *formula*? That is what
update()'s formula method does.
It is rather rare to use expand.model.frame() directly. As ever, we
recommend reading a good book on R as applied to whatever you are trying
to do -- several of them have examples of using update().
On Thu, 30 Sep 2004, David Hugh-Jones wrote:
> Hello,
>
> I am a (relatively) experienced programmer, but new to R.
In short, inexperienced with R or languages like R.
> I have a problem using R 1.9.1. I have fit some data using glm(), from
> within a function:
>
> formula = as.formula(paste(depvarname, "~", rhs),
env=globalenv())
> return (glm(formula, family=binomial(link=logit)))
>
> I have now come back to the formula and want to add some more
> variables to it. So I do:
>
> expand.model.frame(formulaname, ~ new_variable)
>
> but I get the response
>
> Error in eval(expr, envir, enclos) : Object "foreignaid.dummy"
not found
>
> where foreignaid.dummy is my dependent variable. However,
> foreignaid.dummy is clearly visible in the global environment:
>
> > ls(pat="foreignaid.dummy", envir=globalenv())
> [1] "foreignaid.dummy"
> ...
>
> So why is my dependent variable lost?
>
> I have read the earlier comments on the same topic, but they seem to
> indicate that a previous bug was fixed. Am I missing the point about
> scoping?
>
> Any help much appreciated.
>
> David Hugh-Jones
> Essex University Govt Dept
>
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>
>
--
Brian D. Ripley, ripley at stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595