matrix() can't handle NaN (PR#193)
Peter Dalgaard BSA
p.dalgaard@biostat.ku.dk
12 May 1999 11:27:17 +0200
Bill Simpson <wsimpson@gcal.ac.uk> writes:
> > So just which one do
> > you mean? And what are you going to achieve by having essentially a
> > second NA, except to blur the real purposes of NaNs?
>
> Well to me NA means missing value, and it is abuse of NA to use it to
> represent things like 0/0.
And actually the logic is a bit warped:
> NA+NaN
[1] NA
> NaN+NA
[1] NA
> NaN+NaN
[1] NaN
> is.nan(NaN)
[1] TRUE
> is.nan(NA)
[1] FALSE
> is.na(NaN)
[1] TRUE
> The purpose of having NaN to me:
> I am allowed to get an NaN as a result of some operation in R. Let's say I
> then save that in a file, then I read the file in again using read.table.
> In the process of saving and reading it in I lose the NaN. I don't like
> that. It doesn't seem consistent. If the NaN is to be changed, I would
> like to do the changing explicitly myself, so I know what happened to it.
>
> I would also include Inf and -Inf here. These are allowed outputs from R
> operations, so why can't they be read in by read.table? So I am proposing
> that allowable IEEE entities Inf, -Inf, NaN be read in by read.table as
> themselves (not as character strings).
We do allow them as constants in the language itself, so I suppose we
could do it in read.table as well - this really means inside
as.double, I suppose. The prototype does this:
Splus> is.nan(as.double("NaN"))
[1] T
> PS: I remember reading on this list about complex numbers in R. That
> brings in a conflict with IEEE (doesn't it?), because in IEEE,
> sqrt(negative number)->NaN.
> But that is not a NaN if you allow complex numbers (I would think).
> > sqrt(-1)
> Warning: NaNs produced in function "sqrt"
> [1] NaN
>
> Is there a need for an "I" symbol in R?
Nope:
> sqrt(-1+0i)
[1] 0+1i
or, equivalently,
> sqrt(as.complex(-1))
[1] 0+1i
--
O__ ---- Peter Dalgaard Blegdamsvej 3
c/ /'_ --- Dept. of Biostatistics 2200 Cph. N
(*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard@biostat.ku.dk) FAX: (+45) 35327907
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