[Rd] c(NA, 0+1i) not the same as c(as.complex(NA), 0+1i)?
Mikael Jagan
j@g@nmn2 @end|ng |rom gm@||@com
Thu Nov 9 16:51:43 CET 2023
On 2023-11-09 3:13 am, Martin Maechler wrote:
>>>>>> Mikael Jagan
>>>>>> on Wed, 8 Nov 2023 11:13:18 -0500 writes:
>
> > 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 ...
>
> Well, actually, as we now have had the parser accept
> 1i or 7i, 3.14i etc
> I think that it's not the *warning* that is wrong,
> but rather the *result* :
>
Indeed. I realized immediately that I had mistyped, and hoped that readers
would understand what I meant. Yes, as.complex("1i") ought to give 1i and
_not_ NA.
Mikael
> Why should as.complex("1i") be different from one of these?
>
>> 1i
> [1] 0+1i
>> str2lang("1i")
> [1] 0+1i
>> scan(textConnection("1i"), complex())
> Read 1 item
> [1] 0+1i
>>
>
>
> > Mikael
>
> > On 2023-11-07 6:00 am, r-devel-request using 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<maechler using 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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