[ADMB Users] spline smoother on selectivity (even shorter version)

[Mark Payne]

Hi Luis et al,

I am stuck on a very similar problem in a completely different context, where I too end up with postive-definite problems in my hessian. How should this error be interpreted? What can be done to get around this problem? How reliable are the parameter estimates in this case (given that we don't have any uncertainties associated with them)?

Best wishes,

Mark


-----Original Message-----
From: users-bounces at admb-project.org on behalf of Luis Ridao
Sent: Tue 3/1/2011 1:57 PM
To: users at admb-project.org
Subject: [ADMB Users] spline smoother on selectivity (even shorter version)
 
ADMB-help,

Following Dave's suggestion on implementing a spline smoother
on selectivity (in a separable catch-at-age model) I managed to
do something like:

PARAMETER_SECTION
  init_vector log_sel1(1,nNodes)        // nNodes = 5 -> (1,2,3,4,5)
nages = 12 -> (1,2,3,4,5,6,7,8,9,10,11,12)
  sdreport_vector predSel1(1,nages)

for (i=1;i<=nyrs;i++)
  {
  if (i<=36)
  {
    vcubic_spline_function qs(nodes,log_sel1);   // SPLINES
    predSel1=qs(ages);
     }
  else
 .................................
for(i=1;i<=nyrs;i++)
  {
  if (i<=36)
  {
  F(i)=mfexp(log_fy(i))*mfexp(predSel1);
  }
  else
  .................................
The program compiles and runs without problems but when the number of
"nodes"
are changed to another amount (e.g. 6) ADMB complains about Hessian:

"Warning -- Hessian does not appear to be positive definite
Hessian does not appear to be positive definite"

The model template and data files  are attached

Thanks in advance