Spline
Advanced Analysis Library Only
AnalysisLibErrType Spline (double arrayX[], double arrayY[], ssize_t numberOfElements, double b1, double b2, double y2[]);
Purpose
Calculates the second derivatives used by the cubic spline interpolant, given a tabulated function of the form yi = f(xi) for i = 0, 1, . . ., numberOfElements – 1, with xi < xi + 1, and given the boundary conditions firstBoundary and secondBoundary such that the interpolant's second derivative matches the specified values at x0 and xn – 1.
You can use this array with SpInterp to calculate an interpolation value.
Example Code
/* Choose ascending X-values. Pick corresponding Y-values randomly. Set
boundary conditions and specify the cubic spline interpolant to run through the
points. */
double X[100], Y[100], Y2[100], b1, b2;
int n, i;
n = 100;
for(i=0; i<n; i++)
X[i] = i * 0.1;
WhiteNoise (n, 5.0, 17, Y);
b1=0.0;
b2=0.0;
Spline (X, Y, n, b1, b2, Y2);
Parameters
| Input | ||
| Name | Type | Description |
| arrayX | double [] | The known x-values for the planar function; these values must be in ascending order. |
| arrayY | double [] | The known y-values for the planar function. |
| numberOfElements | ssize_t | Number of elements in arrayX, arrayY, and secondDerivatives. |
| firstBoundary | double | The value of the first derivative of the interpolant at the first element of arrayX. |
| secondBoundary | double | The value of the first derivative of the interpolant at the last element of arrayX. |
| secondDerivatives | double [] | Array of second derivatives that specify the interpolant. You can use this array with SpInterp to calculate an interpolation value. These second derivatives represent the continuously differentiable curve to run though the n points (xi, yi). |
Return Value
| Name | Type | Description |
| status | AnalysisLibErrType | A value that specifies the type of error that occurred. Refer to analysis.h for definitions of these constants. |
Additional Information
Library: Advanced Analysis Library
Include file: analysis.h
LabWindows/CVI compatibility: LabWindows/CVI 3.1 and later
Example
Refer to analysis\interp.cws for an example of using the Spline function.