[Rd] NaN in R distribution functions

From: Gregor Gorjanc <gregor.gorjanc_at_bfro.uni-lj.si>
Date: Wed 28 Dec 2005 - 11:25:31 GMT


Dear R developers,

I noticed that core R distribution functions return NaN, when parameter values are out of parameter space. I have looked in source code and found that warnings and return of NaN are done internally in C code. For dgamma.c the line 49 is:

     if (shape <= 0 || scale <= 0) ML_ERR_return_NAN;

OK. How should this be implemented if distribution functions are written directly in R? I came up with this

     if (any(shape <= 0)) {
         warning("shape must be positive")
         return(NaN)
     }

I think that it would be nice that returning NaN for undefined parameter values in distribution functions would also be documented in Writing R Extension.

-- 
Lep pozdrav / With regards,
     Gregor Gorjanc


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University of Ljubljana PhD student Biotechnical Faculty Zootechnical Department URI: http://www.bfro.uni-lj.si/MR/ggorjan Groblje 3 mail: gregor.gorjanc <at> bfro.uni-lj.si SI-1230 Domzale tel: +386 (0)1 72 17 861 Slovenia, Europe fax: +386 (0)1 72 17 888
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"One must learn by doing the thing; for though you think you know it, you have no certainty until you try." Sophocles ~ 450 B.C. ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
Received on Wed Dec 28 22:31:01 2005

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