[Rd] which.max does not work on numeric_version class vectors

[Mikael Jagan]

Moved to Bugzilla as a wishlist item:

     https://bugs.r-project.org/show_bug.cgi?id=18983

Mikael

> Date: Mon, 22 Dec 2025 21:16:11 +0100
> From: Kurt Hornik <Kurt.Hornik using wu.ac.at>
> 
>>>>>> >>>>> Ben Bolker writes:
> 
> Right, but as Gabor already pointed out, now that we have xtfrm (which
> has a numeric_version method) there is no reason why which.max() and
> which.min() should not take advantage of it in the case of classed
> arguments.  
> 
> I'll try to discuss this within R Core: patches welcome :-)
> 
> Best
> -k
> 
>> >   Sorry if this is obvious, but `which.max()` is hard-coded in C, with a
>> > step at the beginning that attempts to coerce the vector to numeric
> 
>> > https://github.com/r-devel/r-svn/blob/5e0a5f013292e56c73360addb61ddaa7d3ca16a2/src/main/summary.c#L1027
> 
>> > Another alternative (your methods are probably better?)
> 
>> > which.max.nv <- function(x) (seq_along(x)[x == max(x)])[1]
> 
>> >    It seems like too much work to change the definition of package versions
>> > (which is a list of integer vectors, under the hood) or to make a generic
>> > S3 method for which.max, given that the workarounds are so easy.
> 
>> >   Also, the documentation explicitly calls out this limitation:
> 
>> > x: numeric (logical, integer or double) vector or an R object
>> >           for which the internal coercion to ‘double’ works whose ‘min’
>> >           or ‘max’ is searched for.
> 
> 
> 
>> > On Sat, Dec 20, 2025 at 10:35 AM Gabor Grothendieck <ggrothendieck using gmail.com>
>> > wrote:
> 
>>> >> versions <- c("9.10", "9.2")
>>> >> nv <- numeric_version(versions)
>>> >> class(nv)
>>> >> ## [1] "numeric_version"
>>> >> 
>>> >> max(nv) # ok
>>> >> ## [1] ‘9.10’
>>> >> 
>>> >> versions[tail(order(nv), 1)] # ok
>>> >> ## [1] "9.10"
>>> >> 
>>> >> sort(nv, decreasing = TRUE)[1] # ok
>>> >> ## [1] ‘9.10’
>>> >> 
>>> >> versions[which.max(xtfrm(nv))] # ok
>>> >> ## [1] "9.10"
>>> >> 
>>> >> versions[which.max(nv)] # error
>>> >> ## Error in which.max(nv) : 'list' object cannot be coerced to type
>>> >> 'double'
>>> >> 
>>> >> 
>>> >> --
>>> >> Statistics & Software Consulting
>>> >> GKX Group, GKX Associates Inc.
>>> >> tel: 1-877-GKX-GROUP
>>> >> email: ggrothendieck at gmail.com
>>> >> 
>>> >> ______________________________________________
>>> >> R-devel using r-project.org mailing list
>>> >> https://stat.ethz.ch/mailman/listinfo/r-devel
>>> >> 
> 
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> 
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> 
> 
>