What I think we need is the number of rows of the model frame *before
subsetting*, so that any further arguments (and there are none such in
Martin's example) of the same length as the response get subsetted.
Berwin's fix is ugly, and I think it can be avoided by using model.frame
to do the work by manipulating ... rather carefully so e.g. col gets read
from the model frame and hence subsetted -- that would also allow col to
be written in terms of other variables in the model frame.
I need to spend more time thinking about this in detail.
Brian
On Mon, 8 Mar 2004 [EMAIL PROTECTED] wrote:
> >>>>> "BeT" == Berwin A Turlach <[EMAIL PROTECTED]>
> >>>>> on Mon, 8 Mar 2004 09:17:51 +0100 (CET) writes:
>
> BeT> Dear all, I noticed the following bug in points.formula
>
> <...>
> BeT> Error in if (length(x) == l) x[s] else x : argument is
> BeT> of length zero
>
> Thank you, Berwin.
> The bug is still present in current "R-1.9.0 alpha"
> and can be demonstrated with the slightly simpler code
>
> roller <-
> data.frame(weight = c(1.9, 3.1, 3.3, 4.8, 5.3, 6.1, 6.4, 7.6, 9.8, 12.4),
> depression = c(2, 1, 5, 5, 20, 20, 23, 10, 30, 25))
> plot( depression ~ weight, data=roller, type="n")
> with(roller, points( depression~weight, subset=1:7 )) # ok
> with(roller, points( depression~weight, subset=8:10)) # ok
> with(roller, points( depression~weight, subset=8:10, col=2))## --> Error
>
> BeT> This seems to be due to the fact that the data used was
> BeT> attached before the call and not specified in the call
> BeT> via the "data" argument.
>
> Yes, using "data =" doesn't show the problem,
> but as you see, the problem also shows for the more recommended
> way of using with() instead of attach()..
>
> BeT> The following patch seems to fix the problem.
>
> *** /home/berwin/lang/R/Courses/3S6/plot.R.orig Tue Sep 2 23:43:42 2003
> --- /home/berwin/lang/R/Courses/3S6/plot.R Mon Mar 8 16:06:32 2004
> ***************
> *** 312,318 ****
> mf <- eval(m, parent.frame())
> if (!missing(subset)) {
> s <- eval(m$subset, data, parent.frame())
> ! l <- nrow(data)
> dosub <- function(x) if (length(x) == l) x[s] else x
> dots <- lapply(dots, dosub)
> }
> --- 312,320 ----
> mf <- eval(m, parent.frame())
> if (!missing(subset)) {
> s <- eval(m$subset, data, parent.frame())
> ! mtmp <- m
> ! mtmp$subset <- NULL
> ! l <- nrow(eval(mtmp, parent.frame()))
> dosub <- function(x) if (length(x) == l) x[s] else x
> dots <- lapply(dots, dosub)
> }
>
> -------------------
>
> Yes, but the resulting code becomes even more ugly.
> doing a second eval(m, ..) just with a slightly modified 'm'...
>
> Though I'll have to leave it to others to find if there is a
> better patch...
>
> Thanks again, Berwin!
> Martin
>
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>
>
--
Brian D. Ripley, [EMAIL PROTECTED]
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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