[Rd] rpois(9, 1e10)

[Spencer Graves]

       This issue arose for me in simulations to estimate confidence, 
prediction, and tolerance intervals from glm(., family=poisson) fits 
embedded in a BMA::bic.glm fit using a simulate.bic.glm function I added 
to the development version of Ecfun, available at 
"https://github.com/sbgraves237/Ecfun".  This is part of a vignette I'm 
developing, available at 
"https://github.com/sbgraves237/Ecfun/blob/master/vignettes/time2nextNuclearWeaponState.Rmd". 
This includes a simulated mean of a mixture of Poissons that exceeds 
2e22.  It doesn't seem unreasonable to me to have rpois output a 
numerics rather than integers when a number simulated exceeds 
.Machine$integer.max.  And it does seem to make less sense in such cases 
to return NAs.


        Alternatively, might it make sense to add another argument to 
rpois to give the user the choice?  E.g., an argument "bigOutput" with 
(I hope) default = "numeric" and "NA" as a second option.  Or NA is the 
default, so no code that relied that feature of the current code would 
be broken by the change.  If someone wanted to use arbitrary precision 
arithmetic, they could write their own version of this function with 
"arbitraryPrecision" as an optional value for the "bigOutput" argument.


       Comments?
       Thanks,
       Spencer Graves


On 2020-01-19 10:28, Avraham Adler wrote:
> Technically, lambda can always be numeric. It is the observations 
> which must be integral.
>
> Would hitting everything larger than maxint or maxlonglong with floor 
> or round fundamentally change the distribution? Well, yes, but enough 
> that it would matter over process risk?
>
> Avi
>
> On Sun, Jan 19, 2020 at 11:20 AM Benjamin Tyner <btyner using gmail.com 
> <mailto:btyner using gmail.com>> wrote:
>
>     So imagine rpois is changed, such that the storage mode of its return
>     value is sometimes integer and sometimes numeric. Then imagine the
>     case
>     where lambda is itself a realization of a random variable. Do we
>     really
>     want the storage mode to inherit that randomness?
>
>
>     On 1/19/20 10:47 AM, Avraham Adler wrote:
>     > Maybe there should be code for 64 bit R to use long long or the
>     like?
>     >
>     > On Sun, Jan 19, 2020 at 10:45 AM Spencer Graves
>     > <spencer.graves using prodsyse.com
>     <mailto:spencer.graves using prodsyse.com>
>     <mailto:spencer.graves using prodsyse.com
>     <mailto:spencer.graves using prodsyse.com>>> wrote:
>     >
>     >
>     >
>     >     On 2020-01-19 09:34, Benjamin Tyner wrote:
>     >     >>
>     >
>      ------------------------------------------------------------------------
>     >     >> Hello, All:
>     >     >>
>     >     >>
>     >     >>         Consider:
>     >     >>
>     >     >>
>     >     >> Browse[2]> set.seed(1)
>     >     >> Browse[2]> rpois(9, 1e10)
>     >     >> NAs produced[1] NA NA NA NA NA NA NA NA NA
>     >     >>
>     >     >>
>     >     >>         Should this happen?
>     >     >>
>     >     >>
>     >     >>         I think that for, say, lambda>1e6, rpois should
>     return
>     >     rnorm(.,
>     >     >> lambda, sqrt(lambda)).
>     >     > But need to implement carefully; rpois should always return a
>     >     > non-negative integer, whereas rnorm always returns numeric...
>     >     >
>     >
>     >            Thanks for the reply.
>     >
>     >
>     >            However, I think it's not acceptable to get an NA from a
>     >     number
>     >     that cannot be expressed as an integer.  Whenever a randomly
>     >     generated
>     >     number would exceed .Machine$integer.max, the choice is between
>     >     returning NA or a non-integer numeric.  Consider:
>     >
>     >
>     >      > 2*.Machine$integer.max
>     >     [1] 4294967294
>     >      > as.integer(2*.Machine$integer.max)
>     >     [1] NA
>     >     Warning message:
>     >     NAs introduced by coercion to integer range
>     >
>     >
>     >            I'd rather have the non-integer numeric.
>     >
>     >
>     >            Spencer
>     >
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