just to make sure you're not doing duplicate work--You get PDL::GSL::CDF when
you install PDL::Stats from CPAN. I don't think the PDFs are there though.
See http://pdl-stats.sourceforge.net/
Derek
On Jun 7, 2012, at 2:31 PM, Tom Nishimura wrote:
> Dear Piddlers,
>
> I'm in the process of binding the GSL random distribution functions
> (since currently only the samplers are implemented, in PDL::GSL::RNG,
> not the pdf/cdf functions).
>
> I'm trying to bind a function whose prototype has a mix of types, like
> so:
>
> double gsl_ran_poisson_pdf (unsigned int k, double mu)
>
> I want to bind it so that it is threadable on both parameters, like:
>
> PDL::gsl_ran_poisson_pdf(long(20), 10.5);
> PDL::gsl_ran_poisson_pdf(long(10), pdl(8,9,10,11,12));
> PDL::gsl_ran_poisson_pdf(long(8,9,10,11,12), pdl(8,9,10,11,12));
>
> My first attempt is the obvious:
>
> pp_def('gsl_ran_poisson_pdf',
> Pars => 'int numdraws(); double lambda(); double [o] out()',
> Code => q{
> $out() = gsl_ran_poisson_pdf( $numdraws(), $lambda() );
> },
> );
>
> This works, but then I started wondering how cognizant people will be
> about passing an integer type as the first parameter, since in Perl
> most people don't worry about types too much. I'd prefer automatically
> rounding floating point values correctly, so the following three lines
> produce the same value. The above will truncate 9.9 to 9. (I'm not
> sure if 10.0 is guaranteed to cast down to the 'properly' to 10,
> or could it possibly to be cast to 9?)
>
> PDL::gsl_ran_poisson_pdf(double(9.9), pdl(8,9,10,11,12));
> PDL::gsl_ran_poisson_pdf(double(10.0), pdl(8,9,10,11,12));
> PDL::gsl_ran_poisson_pdf(double(10.1), pdl(8,9,10,11,12));
>
> Maybe I should drop the type spec from numdraws() in Pars and use the
> type of the loop to decide whether or not to round?:
>
> pp_def('gsl_ran_poisson_pdf2',
> Pars => 'numdraws(); double lambda(); double [o] out()',
> Code => q{
> /* the generic loop type is the type of numdraws, right? */
> types(BSUL) %{
> $out() = gsl_ran_poisson_pdf( $numdraws(), $lambda() );
> %}
> types(FD) %{
> $out() = gsl_ran_poisson_pdf(
> /* need to round numdraws to nearest int */
> ($numdraws() > 0.0) ?
> floor($numdraws() + 0.5) :
> ceil($numdraws() - 0.5),
> $lambda()
> );
> %}
> },
> );
>
> This achieves automatic rounding but seems hackish. Any advice? Should
> I just go with the first version and leave it to the user to be aware of
> the types? Or is there a smarter way of properly rounding floating
> points down to integers? Maybe keep the first one, but write a wrapper
> in Perl?
>
> Also, side question: how come there is no 'unsigned int' type in PDL?
> ushort is the only unsigned int type.
>
> thanks,
> Tom
>
> _______________________________________________
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>
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