[ADMB Users] Question about R2admb

[dave fournier]

On 14-03-31 02:10 PM, John Sibert wrote:

Well it may not  matter much if you just switch in one direction. but 
suppose you want a function like

                      0 if x<1
         f(x)  =   1 if 1<=x<=2
                      0 if x>2


You can do that with.

main()
{
   double e = 0.1;
   interpret_spline sp1(0,1,1,e);
   interpret_spline sp2(1,0,2,e);

   for (double x=0.0;x<=3.0;x+=.01)
   {
     if (x<1.5)
       cout << x << " " << sp1(x) << endl;
     else
       cout << x << " " << sp2(x) << endl;
   }
}




> This seems like a really good idea to me. It is a much better way to 
> implement a step function or threshold functional relation than trying 
> to fart around with various types of sigmoid approximations that may 
> be hard to estimated.
>
> John Sibert
> Emeritus Researcher, SOEST
> University of Hawaii at Manoa
> Honolulu HI (GMT-10)
> 808-294-3842
>
> Visit the ADMB project http://admb-project.org/
>
> On 03/30/2014 08:06 AM, dave fournier wrote:
>> I'm not sure exaclty what is wanted, but it does suggest  that one 
>> may want something like the following function
>> which I suppose could get added to ADMB in some form.
>>
>> It should be
>>
>>                        a if x<=c-e
>>            f(x) =
>>                        b if x>=c+e
>>
>>            f'(x-e)=0
>>            f'(x+e)=0
>>
>>          f is nice for c-e<x<c+e
>>
>> this can be done with a cubic spline.   A nice way is to
>> declare a class to hold the necessary information and a function 
>> object or functor
>> to evaluate the function .  It could be extended to deal with more 
>> general boundary
>> conditions
>>
>>           f'(x-e)=u
>>           f'(x+e)=v
>>
>> with a bit of care.
>>
>>
>>
>>
>> _______________________________________________
>> Users mailing list
>> Users at admb-project.org
>> http://lists.admb-project.org/mailman/listinfo/users
>
>