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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