init()

The init method initializes a new instance of INTERP. It needs as input an interpolation type and two piddles holding the x and y values to be interpolated. The GSL routines require that x be monotonically increasing and a quicksort is performed by default to ensure that. You can skip the quicksort by passing the option {Sort => 0}.

The available interpolation types are :

linear

polynomial

cspline (natural cubic spline)

cspline_periodic (periodic cubic spline)

akima (natural akima spline)

akima_periodic (periodic akima spline)

Please check the GSL documentation for more information.

Usage:

    $blessed_ref = PDL::GSL::INTERP->init($interp_method,$x,$y,$opt);

Example:

    $x = sequence(10);
    $y = exp($x);
    $spl = PDL::GSL::INTERP->init('cspline',$x,$y)
    $spl = PDL::GSL::INTERP->init('cspline',$x,$y,{Sort => 1}) #same as above
    # no sorting done on x, user is certain that x is monotonically increasing
    $spl = PDL::GSL::INTERP->init('cspline',$x,$y,{Sort => 0});

eval()

The function eval returns the interpolating function at a given point. It will barf with an "input domain error" if you try to extrapolate.

Usage:

    $result = $spl->eval($points);

Example:

    my $res = $spl->eval($x)

deriv()

The deriv function returns the derivative of the interpolating function at a given point. It will barf with an "input domain error" if you try to extrapolate.

Usage:

    $result = $spl->deriv($points);

Example:

    my $res = $spl->deriv($x)

deriv2()

The deriv2 function returns the second derivative of the interpolating function at a given point. It will barf with an "input domain error" if you try to extrapolate.

Usage:

    $result = $spl->deriv2($points);

Example:

    my $res = $spl->deriv2($x)

integ()

The integ function returns the integral of the interpolating function between two points. It will barf with an "input domain error" if you try to extrapolate.

Usage:

    $result = $spl->integ($la,$lb);

Example:

    my $res = $spl->integ($la,$lb)