[Rd] Recent changes to as.complex(NA_real_)
Duncan Murdoch
murdoch@dunc@n @end|ng |rom gm@||@com
Fri Sep 22 22:43:43 CEST 2023
Since the result of is.na(x) is the same on each of those, I don't see a
problem. As long as that is consistent, I don't see a problem. You
shouldn't be using any other test for NA-ness. You should never be
expecting identical() to treat different types as the same (e.g.
identical(NA, NA_real_) is FALSE, as it should be). If you are using a
different test, that's user error.
Duncan Murdoch
On 22/09/2023 2:41 p.m., Hervé Pagès wrote:
> We could also question the value of having an infinite number of NA
> representations in the complex space. For example all these complex
> values are displayed the same way (as NA), are considered NAs by
> is.na(), but are not identical or semantically equivalent (from an Re()
> or Im() point of view):
>
> NA_real_ + 0i
>
> complex(r=NA_real_, i=Inf)
>
> complex(r=2, i=NA_real_)
>
> complex(r=NaN, i=NA_real_)
>
> In other words, using a single representation for complex NA (i.e.
> complex(r=NA_real_, i=NA_real_)) would avoid a lot of unnecessary
> complications and surprises.
>
> Once you do that, whether as.complex(NA_real_) should return
> complex(r=NA_real_, i=0) or complex(r=NA_real_, i=NA_real_) becomes a
> moot point.
>
> Best,
>
> H.
>
> On 9/22/23 03:38, Martin Maechler wrote:
>>>>>>> Mikael Jagan
>>>>>>> on Thu, 21 Sep 2023 00:47:39 -0400 writes:
>> > Revisiting this thread from April:
>>
>> >https://stat.ethz.ch/pipermail/r-devel/2023-April/082545.html
>>
>> > where the decision (not yet backported) was made for
>> > as.complex(NA_real_) to give NA_complex_ instead of
>> > complex(r=NA_real_, i=0), to be consistent with
>> > help("as.complex") and as.complex(NA) and as.complex(NA_integer_).
>>
>> > Was any consideration given to the alternative?
>> > That is, to changing as.complex(NA) and as.complex(NA_integer_) to
>> > give complex(r=NA_real_, i=0), consistent with
>> > as.complex(NA_real_), then amending help("as.complex")
>> > accordingly?
>>
>> Hmm, as, from R-core, mostly I was involved, I admit to say "no",
>> to my knowledge the (above) alternative wasn't considered.
>>
>> > The principle that
>> > Im(as.complex(<real=(double|integer|logical)>)) should be zero
>> > is quite fundamental, in my view, hence the "new" behaviour
>> > seems to really violate the principle of least surprise ...
>>
>> of course "least surprise" is somewhat subjective. Still,
>> I clearly agree that the above would be one desirable property.
>>
>> I think that any solution will lead to *some* surprise for some
>> cases, I think primarily because there are *many* different
>> values z for which is.na(z) is true, and in any case
>> NA_complex_ is only of the many.
>>
>> I also agree with Mikael that we should reconsider the issue
>> that was raised by Davis Vaughan here ("on R-devel") last April.
>>
>> > Another (but maybe weaker) argument is that
>> > double->complex coercions happen more often than
>> > logical->complex and integer->complex ones. Changing the
>> > behaviour of the more frequently performed coercion is
>> > more likely to affect code "out there".
>>
>> > Yet another argument is that one expects
>>
>> > identical(as.complex(NA_real_), NA_real_ + (0+0i))
>>
>> > to be TRUE, i.e., that coercing from double to complex is
>> > equivalent to adding a complex zero. The new behaviour
>> > makes the above FALSE, since NA_real_ + (0+0i) gives
>> > complex(r=NA_real_, i=0).
>>
>> No! --- To my own surprise (!) --- in current R-devel the above is TRUE,
>> and
>> NA_real_ + (0+0i) , the same as
>> NA_real_ + 0i , really gives complex(r=NA, i=NA) :
>>
>> Using showC() from ?complex
>>
>> showC <- function(z) noquote(sprintf("(R = %g, I = %g)", Re(z), Im(z)))
>>
>> we see (in R-devel) quite consistently
>>
>>> showC(NA_real_ + 0i)
>> [1] (R = NA, I = NA)
>>> showC(NA + 0i) # NA is 'logical'
>> [1] (R = NA, I = NA)
>> where as in R 4.3.1 and "R-patched" -- *in*consistently
>>
>>> showC(NA_real_ + 0i)
>> [1] (R = NA, I = 0)
>>> showC(NA + 0i)
>> [1] (R = NA, I = NA)
>> .... and honestly, I do not see *where* (and when) we changed
>> the underlying code (in arithmetic.c !?) in R-devel to *also*
>> produce NA_complex_ in such complex *arithmetic*
>>
>>
>> > Having said that, one might also (but more naively) expect
>>
>> > identical(as.complex(as.double(NA_complex_)), NA_complex_)
>>
>> > to be TRUE.
>>
>> as in current R-devel
>>
>> > Under my proposal it continues to be FALSE.
>>
>> as in "R-release"
>>
>> > Well, I'd prefer if it gave FALSE with a warning
>> > "imaginary parts discarded in coercion", but it seems that
>> > as.double(complex(r=a, i=b)) never warns when either of
>> > 'a' and 'b' is NA_real_ or NaN, even where "information"
>> > {nonzero 'b'} is clearly lost ...
>>
>> The question of *warning* here is related indeed, but I think
>> we should try to look at it only *secondary* to your first
>> proposal.
>>
>> > Whatever decision is made about as.complex(NA_real_),
>> > maybe these points should be weighed before it becomes part of
>> > R-release ...
>>
>> > Mikael
>>
>> Indeed.
>>
>> Can we please get other opinions / ideas here?
>>
>> Thank you in advance for your thoughts!
>> Martin
>>
>> ---
>>
>> PS:
>>
>> Our *print()*ing of complex NA's ("NA" here meaning NA or NaN)
>> is also unsatisfactory, e.g. in the case where all entries of a
>> vector are NA in the sense of is.na(.), but their
>> Re() and Im() are not all NA:
>>
>> showC <- function(z) noquote(sprintf("(R = %g, I = %g)", Re(z), Im(z)))
>> z <- complex(, c(11, NA, NA), c(NA, 99, NA))
>> z
>> showC(z)
>>
>> gives
>>
>> > z
>> [1] NA NA NA
>> > showC(z)
>> [1] (R = 11, I = NA) (R = NA, I = 99) (R = NA, I = NA)
>>
>> but that (printing of complex) *is* another issue,
>> in which we have the re-opened bugzilla PR#16752
>> ==>https://bugs.r-project.org/show_bug.cgi?id=16752
>>
>> on which we also worked during the R Sprint in Warwick three
>> weeks ago, and where I want to commit changes in any case {but
>> think we should change even a bit more than we got to during the
>> Sprint}.
>>
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>
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