Re: [Bug-gsl] Re: Interpolation

[Evgeny Kurbatov]

Hi Rhys

On Wed, 24 Nov 2010 09:52:24 -0600
Rhys Ulerich <address@hidden> wrote:

> >> why the interpolating routines become extrapolating sometimes?
> >> Today I spent several hours to find the stupid bug in my program
> >> due to interpolation bounds violation.  When an interpolation
> >> point becomes greater than right bound or lower than left then no
> >> error returns but the routine extrapolates a function value to
> >> that point giving very brave values.
> 
> > That sounds like a good idea, to just hardcode an error for values
> > outside the range,
> 
> Any chance that you'll break everyone who depended on this
> extrapolation "feature"?  Such a check seems like an easy thing for
> the library user to do when/if it makes sense.

I think no chance.  This check has already done in gsl_interp_eval_e
and related procs with _e suffix.  It is strange not to do it in
others.  In addition, it it necessary to clean situation with error
codes returning from interpolation procedures, when the code is
GSL_FAILURE in cspline_eval_deriv and deriv2, and the code
is GSL_EINVAL in linear_eval_deriv.  I'll send the patch in a
coming days when rake an urgent tasks.

Regards,
Evgeny Kurbatov

> 
> - Rhys
>