# CUBSPL

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

## Format

CUBSPL(x,z,id) or CUBSPL(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 = "CUBSPL(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 -1.1000000E+02
</Reference_Spline>
```