Weird Behavior of mean

   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 at 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 at ucla.edu)

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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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