[Rd] New R function is.nana = is.na & !is.nan

[Jan Gorecki]

Hello R-devel,

Best wishes in the new year. I am writing to kindly request new R
function so NA_real_ can be more easily detected.
Currently if one wants to test for NA_real_ (but not NaN) then extra
work has to be done: `is.na(x) & !is.nan(x)`
Required functionality is already at C level so to address my request
there is not that much to do.
Kevin Ushey made a nice summary of current R C api in:
https://stackoverflow.com/a/26262984/2490497
Pasting related part below, extra row added by me is a requested feature.

    +---------------------+
    | C fun    | NaN | NA | R fun
    +---------------------+
    | ISNAN    |  t  | t  | is.na
    | R_IsNaN  |  t  | f  | is.nan
    | ISNA     |  f  | t  | is.na && !is.nan
    | R_IsNA   |  f  | t  | is.na && !is.nan
    +---------------------+
    +---------------------+
    | R fun    | NaN | NA | C fun
    +---------------------+
    | is.na    |  t  | t  | ISNAN
    | is.nan   |  t  | f  | R_IsNaN
    +---------------------+
    | is.nana  |  f  | t  | R_IsNA
    +---------------------+

Strictly speaking, I am asking for a new R function:

    is.nana <- function(x) if (typeof(x)=="numeric")
.Primitive("is.nana") else .Primitive("is.na")

Then probably a copy of C function `do_isnan` as `do_isnana` with a
minor change from `R_IsNaN` to `R_IsNA`.

Best,
Jan Gorecki