delete.response leaves response in attribute dataClasses

Thanks, Bill

Counter-arguments at the end

My feeling that everyone would index dataClasses by name was
wrong. ?I looked through the packages that used dataClasses
and saw code that would break if the first (response) entry
were omitted. ?(I didn't check to see if passing the output
of delete.response to these functions would be appropriate.)
E.g.,
file: AICcmodavg/R/predictSE.mer.r
?##matrix with info on factors
?fact.frame <- attr(attr(orig.frame, "terms"), "dataClasses")[-1]

?##continue if factors
?if(any(fact.frame == "factor")) {
? ?id.factors <- which(fact.frame == "factor")
? ?fact.name <- names(fact.frame)[id.factors] #identify the rows for factors

Some packages create a dataClass attribute for a model.frame
(not its terms attribute) that does not have any names:
file: caper/R/macrocaic.R
? attr(mf, "dataClasses") <- rep("numeric", dim(termFactors)[2])
.checkMFClasses() does not throw an error for that, but it
doesn't do any real checking either.

Most users of dataClasses do pass it to .checkMFClasses() to
compare it with newdata and that doesn't care if you have extra
entries in dataClasses.

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com

I can't understand what your point is.  I agree we can work around the
problem, but why should we have to?

If you confine yourself to the output of "delete.response" applied to
a terms object from a regression, can you point to any package or
usage that depends on leaving the response variable in the dataClasses
attribute?  I can't find one.  In R base, these are all the references
to delete.response:

stats/R/models.R:delete.response <- function (termobj)
stats/R/lm.R:        Terms <- delete.response(tt)
stats/R/lm.R:        Terms <- delete.response(tt)
stats/R/ppr.R:        Terms <- delete.response(object$terms)
stats/R/loess.R:
as.matrix(model.frame(delete.response(terms(object)), newdata,
stats/R/dummy.coef.R:    Terms <- delete.response(Terms)

I've looked it over carefully and predict.lm (in lm.R) would not be
affected by the change I propose. I can't find any usage in loess.R of
the dataClasses attribute.

Furthermore, I can't see how a person would use the dataClasses
attribute at all, after the other markers of the response are
eliminated. How is a method to find which variable is the response,
after response=0?

I'm not disagreeing with you that I can workaround the peculiarity
that the response is left in the dataClasses attribute of the output
object from delete.response.  I'm just saying it is a complication
that programmers should not have to put up with, because I think
delete.response should delete the response from all attributes of a
terms object.

pj

Paul E. Johnson
Professor, Political Science
1541 Lilac Lane, Room 504
University of Kansas