Re: Behavior for conf() different from XSPEC (bug?)

On Mon, Jun 07, 2004 at 10:59 -0400, Nat Butler wrote:
> I was fitting power-laws in both cases.  I found the best fit model and
> then calculated the confidence interval using vconf().  For both cases,
> it's clear that vconf is not minimizing the other parameters.  Here's one
> case:
> 
> best fit model:
> powerlaw(1)
>  idx  param             tie-to  freeze         value         min         max
>   1  powerlaw(1).norm       0     0          22.2139           0       1e+10  
>   2  powerlaw(1).PhoIndex   0     0          2.31315          -2           9  
> 
> then:
> isis> vconf(2)


Yes, there was a bug for the case of 2 variable fit parameters.  
Here's a patch that should fix it:

--- isis-1.1.6/src/fit-chisqrconf.c     Sat May 31 19:09:38 2003
+++ isis-1.1.6/src/fit-chisqrconf.c     Mon Jun  7 11:21:13 2004
_at_email.domain.hidden    par = info->par;
    verbose = info->verbose;

-   sinfo->find_best = (par->npars > 1) ? 1 : 0;
+   sinfo->find_best = (par->npars > 0) ? 1 : 0;

    a.par = ISIS_MALLOC (par->npars * sizeof(double));
    b.par = ISIS_MALLOC (par->npars * sizeof(double));


This fix will be in the next release.

Thanks for reporting that,
-John

--
John C. Houck         MIT Center for Space Research
tel: 617-253-3849           77 Massachusetts Avenue
fax: 617-253-8084          Cambridge, MA 02139-4307
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