[Rd] delete.response() incorrectly handles terms-objects (PR#1327)

[david.meyer@ci.tuwien.ac.at]

Prof Brian D Ripley wrote:
> 
> Thanks, fixed now.
> 
> Why were you calling delete.response on an object with no response, BTW?

I used it in predict.svm(), and the terms-object contained in the svm
model just happens to have no response for the ``one-class
classification'' if svm was called e.g. by:

m <- svm(~a+b).

Because of the second line in delete.response()

    if (length(f) == 3) 
        f[[2]] <- NULL

handling the no-response case, I believed I was allowed to use
delete.response() without checking for this.

> I wonder whether delete.response should not be a no-op in that case (it is
> in S), if there is any reason to handle it at all.

So people will have to check for it before using delete.response() -
this is probably more secure indeed.

-d
> 

-- 
	Mag. David Meyer		Wiedner Hauptstrasse 8-10
Vienna University of Technology		A-1040 Vienna/AUSTRIA
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Statistics and Probability Theory	mail: david.meyer@ci.tuwien.ac.at

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