[Rd] var() with 0-length vector -- docs inconsistent with result
m@echler @ending from @t@t@m@th@ethz@ch
Wed Sep 12 11:50:58 CEST 2018
>>>>> Raubertas, Richard via R-devel
>>>>> on Tue, 11 Sep 2018 18:52:55 +0000 writes:
> R 3.5.1 on Windows 7 The documentation for 'var' says:
> "These functions return 'NA' when there is only one
> observation (whereas S-PLUS has been returning 'NaN'), and
> fail if 'x' has length zero."
Well, that help says much more, notably the paragraph
immediately before the sentence you cite ends saying
Note that (the equivalent of) ‘var(double(0), use = *)’ gives ‘NA’
for ‘use = "everything"’ and ‘"na.or.complete"’, and gives an
error in the other cases.
which is true.
Thank you, Richard, for the report.
The current docs are indeed easily misleading here.
I think that just erasing the ending half-sentence
" , and fail if 'x' has length zero. "
> The function 'sd' (based on 'var') has similar documentation.
indeed... and "much worse", it says
The standard deviation of a zero-length vector (after removal of
‘NA’s if ‘na.rm = TRUE’) is not defined and gives an error.
I propose also just amend the docu there, and do not change
the code (as you Richard also seem favor).
After all, `NA` is also pretty close to "not defined", and in that sense valid.
> However, I get:
> > var(numeric(0))
>  NA
> rather than an error.
> Personally I prefer that basic summary functions like
> 'var' not throw errors even in corner cases. But either
> way, the result and the docs are inconsistent.
> Richard Raubertas
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