Returns either a derivative of a curve or an interpolated value from a curve or surface. The curve is fit exactly through a set of discrete data points using an Akima spline fitting method.
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(Required) Real variable that represents the first independent variable in the spline.
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(Optional) Real variable that represents the second independent variable in the spline.
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(Required) The name of the existing data element spline modeling entity that defines the set of discrete data points to be used for the interpolation.
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(Optional) The order of the derivative to be taken at the interpolated point (integer).
Note: Derivative Order may not be specified when interpolating on a surface; that is, when the Second Independent Variable = 0.
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A spline, spline_1, is defined with discrete data as shown in the following table. The data is then used to generate the interpolation function using the Akima spline fitting method. Since the spline defines a curve rather than a surface, the Second Independent Variable must be set to 0.
In the following example, given the tabular data and a value for the independent variable, the AKISPL returns the interpolated value for the dependent variable:
