[Rd] quantile() type 1 for some ordered factors in R-devel

[Trang Le]

Hi Kurt,

Thank you for fixing quantile(). However, do you think c.factor() can
potentially break more functions? For example, with this new change,
classification from the partykit package using predict() comes back NA
because of this:

https://github.com/cran/partykit/blob/597245ef3dfc98411ce919b74c68ba565f077c47/R/party.R#L500

I understand that most of the fixes will probably be simple with
as.numeric() or as.integer(), but tracing down these breaks can be
time-consuming <https://twitter.com/trang1618/status/1260906905041432578>.
What about a warning whenever code that would trigger c.factor() is called?
This way users are given a chance to update packages and code.

Thanks,
Trang

On Wed, May 20, 2020 at 1:53 AM Kurt Hornik <Kurt.Hornik using wu.ac.at> wrote:

> >>>>> Tobias Rockel writes:
>
> Thanks for spotting this, and also to Hadley for reporting to me
> directly.
>
> Fixed now with c78501.
>
> Best
> -k
>
> > Hi,
> > In R-devel (2020-05-17 r78478) quantile() type 1 seems to behave a little
> > bit strange for some ordered factors:
> > quantile(factor(1:3, ordered = TRUE), 0.5, type = 1)
> > returns “2” as expected. But
> > quantile(factor(2:4, ordered = TRUE), 0.5, type = 1)
> > returns “4” and
> > quantile(factor(3:5, ordered = TRUE), 0.5, type = 1)
> > returns “NA”. Furthermore, the function returns “NA” for calls like
> > quantile(factor(c("a", "b", "c"), ordered = TRUE), 0.5, type = 1)
>
> > In R 4.0.0 everything seems fine (return values “2”, “3”, “4”, “b”). If
> the
> > vectors are treated as numeric, everything seems to work fine in R-devel,
> > too. For example
> > quantile(3:5, 0.5, type = 1)
> > returns “4” in R-devel and R 4.0.0.
>
> > Best regards,
> > Tobias Rockel
>
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>
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