[ADMB Users] Writing functions for object type df1b2

[H. Skaug]

Hi Coilin,

Thanks for raising this issue. What you ask about is by no means obvious and
needs documentation.

Yes, the code can be put in the GLOBAL_Section as you suggest.
As an example I included a new function gammln2():

GLOBALS_SECTION

 #include <df1b2fun.h>

 df1b2variable gammln2(const df1b2variable& z)
 {
   return gammln(z);
 }

 dvariable gammln2(const dvariable& z)
 {
   return gammln(z);
 }

The reason I need two versions is that gammln2 is not allready
in ADMB. For cumd_gamma() you would only need
to include the df1b2variable version.

Regards,

Hans

PS You are probably aware that the inverse function
inv_cumd_gamma(const df1b2variable& _y,const df1b2variable& _a)
is allready implemented.

On Tue, Sep 1, 2009 at 1:01 PM, Coilin Minto<mintoc at mathstat.dal.ca> wrote:
> Dear ADMB users,
>
> The ADMB-RE documention details that not all ADMB functions are implemented
> in ADMB-RE yet. I was unable to find documentation for how to write my own
> and would like to ask for a newbie pointer to such documentation or if it
> would be possible to work through an example?
>
> The specific function I would like to use is the cdf for the gamma
> distribution (cumd_gamma in ADMB). When the value (and shape) of X are of
> type df1b2 an error message is returned that cumd_gamma is not yet
> implemented.
>
> Is it acceptable/possible to write functions for df1b2 types in the
> GLOBALS_SECTION, perhaps by using pre-exisiting functions that work for
> other object types? I see that Prof. Bolker implements a power function that
> returns a df1b2 type vector in
>
> http://groups.google.com/group/admb-users/browse_thread/thread/1aff3682f7a6b68c#
>
> The "pow" function used in the loop in this code is implemented for single
> value df1b2 but what about when this is not yet implemented?
>
> Thank you for any guidance and my apologies if this question is ignorant of
> the basic facets of what goes on under the hood.
>
> Sincerely,
> Coilin Minto
>
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