So, to summarize, the open questions are:
(1) Should as.complex(NA_character_) give complex(r=NA_real_, i=0)
instead of NA_complex_?
(2) Should the first argument in c(NA, x) and c(NA_integer_, x),
where typeof(x) == "complex", be promoted to complex(r=NA_real_, i=0)
instead of NA_complex_?
My opinions:
(1) No. The imaginary part of the result of parsing the strings "<b>i",
"<a>+<b>i", and "<a>-<b>i" can be nonzero.
Consider, e.g., Im(eval(str2lang("0+1i"))) and Im(as.complex("0+1i")).
If NA_character_ means "a string with unknown content", then we should
not assume that the string is parsed as a real number.
(2) Yes. I'd very much like to preserve the identity of c(Im(NA), Im(x))
and Im(c(NA, x)) for atomic (excluding raw, character) vectors 'x'.
And while typing this response I noticed the following in current R-devel and
current R-patched:
> 0+1i
[1] 0+1i
> 1i
[1] 0+1i
> as.complex("0+1i")
[1] 0+1i
> as.complex("1i")
[1] NA
Warning message:
NAs introduced by coercion
That warning seems wrong to me ...
Mikael
On 2023-11-07 6:00 am, r-devel-requ...@r-project.org wrote:
Michael Chirico
on Mon, 6 Nov 2023 23:18:40 -0800 writes:
> Thanks Martin. My hang-up was not on what the outcome of as.complex(NA)
> should be, but rather, how I should read code like c(x, y) generally.
Till
> now, I have thought of it like 'c(x, y)' is c(as(x, typeof(y)), y)` when
> "type(y) > type(x)". Basically in my mind, "coercion" in R <->
> as.<newtype>(.) (or coerceVector() in C).
> So I tracked down the source (which admittedly has been this way for much
> longer than the present discussion) to see what exactly c() is doing in
> this case:
>https://github.com/r-devel/r-svn/blob/71e7480b07767f3b7d5c45a4247959aa4d83d910/src/main/bind.c#L418-L425
> And indeed! It's not "coercion" in the sense I just described... there's
a
> branch for the 'x == NA_LOGICAL' case to_convert_ to NA_complex_.
Yes; "of course" ... still, I did not answer your main question,
as you did ask +/- if c() should not get an adjustment to the
new as.complex(<numeric-alike>) |--> (Re = NA, Im = 0)
behavior.
And that is still a valid open question. ... contrary to what I
wrote yesterday; sorry for that "answering a different
question".
Martin
> On Mon, Nov 6, 2023 at 3:08 AM Martin
Maechler<maech...@stat.math.ethz.ch>
> wrote:
>> >>>>> Michael Chirico
>> >>>>> on Sun, 5 Nov 2023 09:41:42 -0800 writes:
>>
>> > This is another follow-up to the thread from September
>> > "Recent changes to as.complex(NA_real_)".
>>
>> > A test in data.table was broken by the changes for NA
>> > coercion to complex; the breakage essentially comes from
>>
>> > c(NA, 0+1i)
>> > # vs
>> > c(as.complex(NA), 0+1i)
>>
>> > The former is the output we tested against; the latter is
>> essentially (via
>> > coerceVector() in C) what's generated by our data.table::shift()
>>
>> > However, these are now (r85472) different:
>>
>> > Im(c(NA, 0+1i))
>> > # [1] NA 1
>> > Im(c(as.complex(NA), 0+1i))
>> > # [1] 0 1
>>
>>
>> > The former matches the behavior of directly using NA_complex_:
>>
>> > Im(c(NA_complex_, 0+1i))
>> > # [1] NA 1
>>
>> > On R4.3.2, they both match the NA_complex_ behavior:
>> > Im(c(NA, 0+1i))
>> > # [1] NA 1
>> > Im(c(as.complex(NA), 0+1i))
>> > # [1] NA 1
>>
>> > Is this intended behavior, does something need to be updated for c()
>> as
>> > well?
>>
>> > Certainly it's messing with my understanding of how c() behaves,
>> e.g. in ?c
>>
>> >> All arguments are coerced to a common type which is the type of the
>> > returned value
>>
>> I think you have confused yourself, and everything behaves as expected:
>>
>> As we now have (in R-devel, since {r85233 | maechler | 2023-09-29 })
>>
>> • ‘as.complex(x)’ now returns ‘complex(real=x, imaginary=0)’
>> for_all_ numerical and logical ‘x’, notably also for ‘NA’
>> or ‘NA_integer_’.
>>
>> ==> as.complex(NA) is indeed complex(real = NA, imaginary = 0)
>>
>> And now, in your
>>
>> c(as.complex(NA), 0+1i)
>>
>> you are calling c() on two complex numbers, i.e., there is*no* coercion
>> (and c(.) is rather "trivial"), and the same is true for
>>
>> c(NA_complex_, 0+1i)
>>
>>
>> However, in 85233, I had only modified & added examples to ?as.complex,
>> and now have added more (corresponding to the above NEWS entry);
-> svn rev 85475
>>
>> .............
>>
>> The underlying "dilemma" that nobody can help us with is that
>> "almost infinitely" many different complex numbers z fulfill
>> is.na(z) |--> TRUE
>> and only one of them is NA_complex_ and that may be unintuitive.
>>
>> OTOH, we already have for the doubles that there are at least two
>> different x fulfulling is.na(x), namely NaN and NA
>> and from C's point of view there are even considerably more
>> different NaN's .. but now I'm definitely digressing.
>>
>> Martin
>>
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