Natural cubic spline option of spline in linad99/vspline.cpp

[yukio-takeuchi]

Although it is not advertised well spline function implemented in ADMB in linad99/vvspline.cpp allows users to model natural cubic spline (2nd derivative of boundary nodes is set to zero) as an alternative of use of 1st derivative of boundary nodes. This can be accomplished by setting yp1 and ypn of function spline to >0.99e30.

/** \ingroup cub_spline
 *  Cubic spline interpolation.
 *
 * \param _x array of abscissa
 * \param _y array of corresponding values \f$y_i=f(x_i)\f$
 * \param yp1 value of the first derivative of \f$f\f$ at the left
 *        end point
 * \param ypn value of the first derivative of \f$f\f$ at the right
 *        end point
 * \return an array containing the second derivatives
*/
dvar_vector spline(const dvector &_x,const dvar_vector&_y,dvariable yp1,
    dvariable ypn)

It may be worthwhile if this information is included somewhere in documentation.

[johnoel]

Is this okay?

/** \ingroup cub_spline
 * Cubic spline interpolation allows users to model natural cubic spline (2nd derivative of boundary nodes is set to zero) as 
 * an alternative of use of 1st derivative of boundary nodes. This can be accomplished by setting yp1 and ypn of function 
 * spline to >0.99e30.
...

[yukio-takeuchi]

I can go with you. Thank you for your quick work.

[johnoel]

Done in revision fe10b9d.