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NOTAKNOT_SPLINE

Creates an interpolated curve from input points with a specified number of values. Interpolates using the Not-a-knot cubic spline.
The length of the Independent Data array must be the same as the Dependent Data array.

Format

NOTAKNOT_SPLINE (Independent Data, Dependent Data, Number of Output Values)

Arguments

 
Independent Data
A 1xN array of x values for the curve to be interpolated. The x values of the points must be in ascending order, and the length of the array must be greater than or equal to 4.
Dependent Data
A 1xN array of y values for the curve to be interpolated.
Number of Output Values
The number of values to be generated in the output array.

Example

The following function interpolates a set of four points with ordinal values from 1 to 4 and abscissal values as shown, into a series of 10 abscissal values:
 
Function
NOTAKNOT_SPLINE({1, 2, 3, 4}, {0, 2, 1, 3}, 10)
Result
{0.0, 1.370, 1.963, 2.0, 1.704, 1.296, 1.0, 1.037, 1.630, 3.0}
To compute the ordinal values for these splined values, you can use the SERIES2 function as follows:
 
Function
SERIES2(1, 4, 10)
Result
{1.0, 1.333, 1.667, 2.0, 2.333, 2.667, 3.0, 3.333, 3.667, 4.0}
Learn more about matrix/array functions.