Re: [R] Use of expand.model.frame()

[Thomas Lumley]

On Sat, 1 Jan 2005, Gabor Grothendieck wrote:
Look at the source of expand.model.frame.
The second line of expand.model.frame uses the data component of mod$call
and if its not there expand.model.frame chokes.  As a workaround check
if its missing and supply it yourself:
if (is.null(mod$call$data)) mod$call$data <- environment(formula(mod))
expand.model.frame(mod, "z")
expand.model.frame should probably be doing that itself.
No, it shouldn't.
It should be setting data to as.list(NULL) if it is NULL.
I am surprised to find that
 y<-1:10
eval(quote(y), NULL, .GlobalEnv)
Error in eval(expr, envir, enclos) : Object "y" not found
eval(quote(y), as.list(NULL), .GlobalEnv)
 [1]  1  2  3  4  5  6  7  8  9 10
eval(quote(y), as.data.frame(NULL), .GlobalEnv)
Error in eval(quote(y), as.data.frame(NULL), .GlobalEnv) :
        attempt to set an attribute on NULL
The third of these is definitely a bug, and I thought the first used to 
work (and that I would have noticed when writing expand.model.frame if it 
didn't).

        -thomas
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