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. By default it will barf if you try to extrapolate, to comply silently if the point to be evaluated is out of range pass the option {Extrapolate => 1}

Usage:

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

Example:

    my $res = $spl->eval($x)
    $res = $spl->eval($x,{Extrapolate => 0}) #same as above
    # silently comply if $x is out of range
    $res = $spl->eval($x,{Extrapolate => 1})

deriv()

The deriv function returns the derivative of the interpolating function at a given point. By default it will barf if you try to extrapolate, to comply silently if the point to be evaluated is out of range pass the option {Extrapolate => 1}

Usage:

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

Example:

    my $res = $spl->deriv($x)
    $res = $spl->deriv($x,{Extrapolate => 0}) #same as above
    # silently comply if $x is out of range
    $res = $spl->deriv($x,{Extrapolate => 1})

deriv2()

The deriv2 function returns the second derivative of the interpolating function at a given point. By default it will barf if you try to extrapolate, to comply silently if the point to be evaluated is out of range pass the option {Extrapolate => 1}

Usage:

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

Example:

    my $res = $spl->deriv2($x)
    $res = $spl->deriv2($x,{Extrapolate => 0}) #same as above
    # silently comply if $x is out of range
    $res = $spl->deriv2($x,{Extrapolate => 1})

integ()

The integ function returns the integral of the interpolating function between two points. By default it will barf if you try to extrapolate, to comply silently if one of the integration limits is out of range pass the option {Extrapolate => 1}

Usage:

    $result = $spl->integ($a,$b,$opt);

Example:

    my $res = $spl->integ($a,$b)
    $res = $spl->integ($a,$b,{Extrapolate => 0}) #same as above
    # silently comply if $a or $b are out of range
    $res = $spl->eval($a,$b,{Extrapolate => 1})