>>>>> "HenrikB" == Henrik Bengtsson <[email protected]>
>>>>> on Sat, 22 Aug 2009 08:34:51 -0700 writes:
HenrikB> On Sat, Aug 22, 2009 at 1:22 AM, Petr Savicky<[email protected]>
wrote:
>> On Sat, Aug 22, 2009 at 12:00:44AM +0200, Martin Maechler wrote:
>>> I have taken up the issue now,
>>> and after thinking, studying the source, trying to define a
>>> 'method = <string>' argument, came to the conclusion that both
>>> the implementation and documentation (and source code
"self-explanation")
>>> are easiest to program, maintain, and understand,
>>> if I introduce explicit binary switches,
>>> so I now propose the following R-level interface which keeps
>>> the current behavior the default:
>>>
>>> >> Usage:
>>> >>
>>> >> identical(x, y, num.EQ = TRUE, one.NA = TRUE, attrib.asSet =
TRUE)
>>> >>
>>> >> Arguments:
>>> >>
>>> >> x, y: any R objects.
>>> >>
>>> >> num.EQ: logical indicating if ('double' and 'complex' non-'NA')
>>> >> numbers should be compared using '==', or by bitwise
>>> >> comparison. The latter (non-default) differentiates
between
>>> >> '-0' and '+0'.
>>> >>
>>> >> one.NA: logical indicating if there is conceptually just one
numeric
>>> >> 'NA' and one 'NaN'; 'one.NA = FALSE' differentiates bit
>>> >> patterns.
>>> >>
>>> >> attrib.asSet: logical indicating if 'attributes' of 'x' and 'y'
should
>>> >> be treated as _unordered_ tagged pairlists ("sets"); this
>>> >> currently also applies to 'slot's of S4 objects. It may
well
>>> >> be too strict to set 'attrib.asSet = FALSE'.
HenrikB> My only comment is to make the argument notation a bit more
consistent:
HenrikB> (num.Eq, one.NA, attrib.as.set)
HenrikB> or
HenrikB> (numEq, oneNA, attribAsSet)
thank you. I think I'd prefer the (older style) with "."
{and I had only one "." in all options},
and yes, I agree that these are a bit more consistent.
HenrikB> Also, maybe "single" instead of "one".
yeaah.. that's possibly better...
Other votes (on this part)?
>> I appreciate having several binary switches. Besides the arguments above,
>> this is also useful for an interactive use of identical(), for example,
>> for debugging purposes. If there is a difference between objects, then
>> the switches allow to get more information concerning what is the type
>> of the difference.
exactly, thanks..
>>> I'm open for better names of arguments, but will not accept "_"
>>> in the argument names {just my taste; no reason for argueing...}.
>>
>> I would slightly prefere one.NaN instead of one.NA.
>> In IEEE 754 terminology, R's 'NA's are a subset of
>> 'NaN's. So. NaN is a bit more general notion, although in
>> R, the sets of 'NA's an 'NaN's are disjoint. Moreover,
>> the name one.NaN specifies more clearly, that the issue
>> is important only for numeric types and not, for example,
>> for integer.
>>
>> Petr.
You are right of course about IEEE NaN's,
and also the fact that there *are* non-numeric NAs in R.
However, in the R world, 'NA' is much more known to users,
and much more importantly,
> is.na(NaN)
[1] TRUE
> is.nan(NA)
[1] FALSE
so in R, (the) NaN is rather a special case of NA.
Additionally, 'NA' is considerably faster to type than 'NaN'..
Consequently, I'd rather keep that.
Thanks again, Petr and Henrik, for your feedback!
Martin
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