[R] the woes of NA

[Peter Dalgaard]

Galkowski, Jan wrote:
> Joyful.
>
> I'm adapting a FORTRAN 77 package for use with R.  Pretty
> straightforward.  
>
> Except for a glitch it took me some time to figure out.  This existing
> package has subroutines which have parameters called "NA". So, I called
> subroutines like
>
> bnodes <- function(n, lst, lptr, lend, nodes, nb, na, nt)
> {
>   ensure.all.numeric(list(n, lst, lptr, lend, nodes, nb, n.a, nt), 
>                      "all arguments to -bnodes- must be numeric")
>   out <- .Fortran("bnodes", N=as.integer(n), LIST=as.integer(lst),
>                   LPTR=as.integer(lptr), LEND=as.integer(lend),
> NODES=as.integer(nodes),
>                   NB=as.integer(nb), NA=as.integer(na),
> NT=as.integer(nt))
>   return(out[5:8])
> }
>
> I had called routines successfully before, so I couldn't figure out what
> was wrong.  By elimination, I discovered that the parameter pass
>
>     NA=as.integer(na)
>
> was to blame.  So, thinking the right-hand-side (R's world) was the
> problem, even if "na" wasn't recognized as "not available", I changed
> to:
>
> bnodes <- function(n, lst, lptr, lend, nodes, nb, n.a, nt)
> {
>   ensure.all.numeric(list(n, lst, lptr, lend, nodes, nb, n.a, nt), 
>                      "all arguments to -bnodes- must be numeric")
>   out <- .Fortran("bnodes", N=as.integer(n), LIST=as.integer(lst),
>                   LPTR=as.integer(lptr), LEND=as.integer(lend),
> NODES=as.integer(nodes),
>                   NB=as.integer(nb), NA=as.integer(n.a),
> NT=as.integer(nt))
>   return(out[5:8])
> }
>
> No win.  I would only be happy if I used
>
> bnodes <- function(n, lst, lptr, lend, nodes, nb, n.a, nt)
> {
>   ensure.all.numeric(list(n, lst, lptr, lend, nodes, nb, n.a, nt), 
>                      "all arguments to -bnodes- must be numeric")
>   out <- .Fortran("bnodes", N=as.integer(n), LIST=as.integer(lst),
>                   LPTR=as.integer(lptr), LEND=as.integer(lend),
> NODES=as.integer(nodes),
>                   NB=as.integer(nb), NAA=as.integer(n.a),
> NT=as.integer(nt))
>   return(out[5:8])
> }
>
> and had to actually change the FORTRAN code to comply.
>
> Sounds to me like there's a little room for improvement here.  Should be
> documented anyway.
>   
Do the argument names even get used on the Fortran side?? AFAIK, it only 
matters for labeling the result.

Anyways, this has nothing to do with "not available", a name like PACK 
would get you equally confused. You are being bitten by partial argument 
matching: NA matches NAOK. One workaround is to add NAOK=FALSE 
explicitly to the call. Or just use lowercase names.

-- 
   O__  ---- Peter Dalgaard             Øster Farimagsgade 5, Entr.B
  c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
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~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)                  FAX: (+45) 35327907