[Rd] Possible bug in termplot function (stats package) ?

[peter dalgaard]

On Jun 6, 2011, at 17:15 , Joris Meys wrote:

> Hi all,
> 
> I noticed some very odd behaviour in the termplot function of the
> stats package due to the following lines :
> 
> 18.    if (is.null(data))
> 19.       data <- eval(model$call$data, envir)
> 
> This one will look in the global environment, and renders the two
> lines after this
> 
> 20.   if (is.null(data))
> 21.        data <- mf
> 
> completely obsolete. If nothing is found, an error is returned. If
> anything is found, data won't be NULL, so line 20, when reached, will
> always return FALSE. Can it be that lines 18 and 19 should be removed
> from the function?


I think this is a false assumption. What keeps model$call$data from being NULL? 

No comments on the remainder, except that it wouldn't be the first time a wrapper function got into trouble with environments and modelling functions... 

> 
> This gives especially problems when called from other plot functions
> on models made with wrapper functions. One example :
> 
> Data <- data.frame(
> x1=rnorm(100),
> x2=rnorm(100,3,2),
> y=rnorm(100)
> )
> form <- as.formula(y~x1+x2)
> test <- lm(form, data=Data)
> termplot(test)
> 
> wrapper <- function(ff,x){
> tt <- lm(ff,data=x)
> }
> test2 <- wrapper(form,Data)
> termplot(test2)
> 
> For the non-smooth terms, termplot is called. In the first example,
> this works perfectly well. In the second example, it either returns "x
> not found" (when there is no x variable in the global) or "x2 not
> found" when there is an x variable.
> 
> If both lines mentioned earlier are erased from the function, it works
> as expected in this example code. Using the model frame seems the
> logic choice here, I have no clue why one would want to look in the
> global environment for the data related to a model.
> 
> Cheers
> Joris
> 
> -- 
> Joris Meys
> Statistical consultant
> 
> Ghent University
> Faculty of Bioscience Engineering
> Department of Applied mathematics, biometrics and process control
> 
> tel : +32 9 264 59 87
> Joris.Meys at Ugent.be
> -------------------------------
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-- 
Peter Dalgaard
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Email: pd.mes at cbs.dk  Priv: PDalgd at gmail.com