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

[Ben Bolker]

  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'
>
>
> --
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