[ADMB Users] Question about R2admb

[Ben Bolker]

On 14-03-27 10:20 AM, Ximing Xu wrote:
> Dear Professor Bolker,
> 
> 
> I am using  R2admb  to fit a state-space model  with my own TPL file.
> 
> In the TPL file ,  we have the following function:
> 
> 
> SEPARABLE_FUNCTION void cond_nllo(const dvariable& deloy,const dvariable& del1y)
> 
>   nll += kterm + 0.5*square(deloy);
>   nll += kterm + 0.5*square(del1y);
> 
> 
> 
> where kterm is some predefined constant, and nll is the objective funtion to be minimized.
> 
> 
> Now I would like to change  nll to be
> 
> 
> nll += kterm + 0.5*square(deloy)*(deloy<=1.4)   with a logical operator .
> 
> 
> Then the TPL file  can not be compiled anymore. I also found that the mathematical operations
> 
> such as + - * / work for deloy but the modulus operator % does not work on it.
> 
> 
> Do you know if there is any way to solve this problem?    Thank you very much.
> 
> 
> 
> Best,
> 
> 
> Ximing

  I'm not 100% sure, but I strongly suspect this is a generic ADMB
question rather than an R2admb-specific question -- that is, it would
apply whether or not you were using the R2admb interface.  I'm taking
the liberty of cc'ing it there. You can probably do something like

  int thresh;
  thresh = (deloy <=1.4 ? 1 : 0 );  // ternary operator

 or perhaps

  thresh = (int)(deloy<=1.4)

(these are two standard C idioms for converting a logical expression to
a 0/1 value).

  I don't know offhand why the modulus operator doesn't work, but
possibly because it is a non-differentiable operator and thus hasn't
been defined in ADMB?  (I searched the ADMB manual for "modulus" and for
"%" used in this context and didn't find it ...

 If you try to compile your model outside of R (i.e. using the
command-line tools rather than R2admb) and find it *does* work from the
command line but not via R2admb, feel free to bug me again.


  good luck,

  Ben Bolker