FITSPL

Returns the interpolated value or n-th derivative of the interpolated value of the Reference_Spline element.

Format

FITSPL(x, z, id) or FITSPL(x, 0, id, n)

Arguments

x
The independent variable of the curve.
z
The independent variable z of the surface. Use z = 0 if only one curve is being defined.
id
The ID of the Reference_Spline element.
n
The order of the derivative desired. Not applicable with surfaces. Must lie between 0 and 2.

Example

<Force_Scalar_TwoBody
   id             = "301001"
   type           = "Force"
   i_marker_id    = "10506"
   body1_id       = "105"
   j_marker_id    = "10706"
   body2_id       = "107"
   val_expression = "FITSPL(DM(10503,10703),0,301002)"
/>
<Reference_Spline
    id                  = "301002"
    num_xy_pair         = "5"
    linear_extrap       = "FALSE">
                          0.0000000E+00  -2.2000000E+02
                          2.0000000E+02  -2.2000000E+02
                          2.3000000E+02  -2.2000000E+02
                          3.7322400E+02  -1.1000000E+02
                          5.0000000E+02  -0.1000000E+02
                          5.1000000E+02  -1.2000000E+02
                          6.0000000E+02  -1.3300000E+02
</Reference_Spline>

Comments

  1. FITSPL is based on the b-spline representation as implemented by the FITPACK in NETLIB (http://www.netlib.org/fitpack/).
  2. Algorithm details can be found in "Curve and Surface Fitting with Splines, Monographs on Numerical Analysis" by Paul Dierckx, Oxford University Press, 1993.