[R] Weird Behavior of mean

[Ben Bolker]

   Thanks, I had missed/forgotten the fact that there is also an 
inconsistency between mean.default() and sd().

   sd() calls var(), which evaluates if(na.rm) [i.e., it will try to 
coerce `na.rm` to logical rather than testing isTRUE]

  IM(H?)O, it would be best for both mean.default() and sd() to use 
if(isTRUE(as.logical(na.rm))) -- this converts NULL, numeric(0), zero 
numeric values, etc. to FALSE, non-zero numeric values (including 
complex numbers not equal to 0+0i) to TRUE ... fails on un-coerceable 
stuff like functions, environments ...


‘as.logical’ attempts to coerce its argument to be of logical
      type.  In numeric and complex vectors, zeros are ‘FALSE’ and
      non-zero values are ‘TRUE’.  For ‘factor’s, this uses the ‘levels’
      (labels).  Like ‘as.vector’ it strips attributes including names.
      Character strings ‘c("T", "TRUE", "True", "true")’ are regarded as
      true, ‘c("F", "FALSE", "False", "false")’ as false, and all others
      as ‘NA’.


On 2024-12-13 5:43 p.m., Bert Gunter wrote:
> Ivo, et al.:
> --IMHO only ... and with apologies for verbosity
> 
> Defining, let alone enforcing, "consistent behavior" can be a
> philosophical conundrum: what one person deems "consistent" behavior
> for a function across different data structures and circumstances may
> not be the same as another's. While you may consider the issue clear
> here, a glance at the source code shows that may not necessarily be
> the case: mean() is an S3 generic, but sd() is derived from var()
> which is in turn based on cov(), for which NA handling is more
> complex.
> 
> Anyway, for me, the only defensible standard should be is that the
> *documented* behavior for overloaded function names is that they
> should be accurately documented for each use case, whether or not the
> semantics conform to any particular paradigm of consistency. By this
> standard, I think mean() is behaving correctly, as its Help page says:
> 
> na.rm
> a *logical* evaluating to TRUE or FALSE indicating whether NA values
> should be stripped before the computation proceeds. [emphasis added]
> Note: *not* a value that can be *coerced* to logical, but an actual
> logical expression.
> 
> But sd() is not, as its Help page says:
> na.rm
> logical. Should missing values be removed?
> Note: So seemingly same as above, but as you noted, will work for
> values that can be coerced to logical and not just actual logical
> expressions.
> 
> Cheers,
> Bert
> 
> 
> 
> On Fri, Dec 13, 2024 at 11:43 AM ivo welch <ivo.welch using ucla.edu> wrote:
>>
>> isn't this still a little R buglet?  I have overwritten T (even if my
>> schuld [franconian], it is not that uncommon an error, because T is also a
>> common abbreviation for the end of a time series; namespace pollution in R
>> can be quite annoying, even though I understand that it is convenient in
>> interactive mode).  Nevertheless, I am passing into mean() a positive
>> number for na.rm, and by definition, a positive number still means TRUE.
>>   besides, sd() and mean() should probably treat this similarly, anyway.  I
>> do see the argument that functions cannot be proof against redefinitions of
>> all sorts of objects that they can use.    more philosophically, some
>> variables should not be overwritable, or at least trigger a warning.
>>
>> As Dante wrote, Abandon all hope ye who enter R.
>>
>> --
>> Ivo Welch (ivo.welch using ucla.edu)
>>
>>          [[alternative HTML version deleted]]
>>
>> ______________________________________________
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> 
> ______________________________________________
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-- 
Dr. Benjamin Bolker
Professor, Mathematics & Statistics and Biology, McMaster University
Director, School of Computational Science and Engineering
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