The Interpolation function calculates the linear or cubic-spline interpolated Y value based on a desired X value and a range of known X and Y values. The interpolation function can be used in conjunction with the various option models.
| Interpolation | (InterpolationType, Xrange, Yrange, ValueX) | 
| Argument | Description | 
| InterpolationType | Alphanumeric value indicating the interpolation type or model: Linear = 0 or "L" (case insensitive) Cubic Spline = 1 or "C" (case insensitive) | 
| Xrange | The range of ascending and unique (non-duplicate) known X values. The size of the array, i.e. the number of values within it, must be the same as the Yrange array. | 
| Yrange | The range of known Y values, where the size of the array must be the same as the Xrange. | 
| ValueX | The input value for the X coordinate whereby a Y value is desired and the return value of the function. | 
Example
| Example: Linear and Cubic Spline Interpolation Calculate the linear and cubic spline interpolation and graph the results give the following table of known X and Y values at the Desired X values below. So, | 
| Input | 
 | Output | |||
| Known X | Known Y | 
 | Desired X | Linear Interpolation | Cubic Spline Interpolation | 
| 0.500 | 3.250 | 
 | 0.500 | 3.250 | 3.250 | 
| 1.000 | 3.625 | 
 | 1.500 | 3.792 | 3.865 | 
| 2.500 | 4.125 | 
 | 2.500 | 4.125 | 4.125 | 
| 4.750 | 4.375 | 
 | 3.500 | 4.236 | 4.426 | 
| 6.250 | 3.250 | 
 | 4.500 | 4.347 | 4.464 | 
| 9.500 | 3.125 | 
 | 5.500 | 3.813 | 3.853 | 
| 
 | 
 | 
 | 6.500 | 3.240 | 3.099 | 
| 
 | 
 | 
 | 7.500 | 3.202 | 2.807 | 
| 
 | 
 | 
 | 8.500 | 3.163 | 2.875 | 
| 
 | 
 | 
 | 9.500 | 3.125 | 3.125 | 

For a further example on this model see the included Excel Template located in the root directory of the add-in. This example can be accessed through the Utility Template menu item after the add-in has been installed properly.
A list of all of the possible Error Messages is included for convenience.