PolyFitEx
- Updated2023-02-21
- 2 minute(s) read
PolyFitEx
Advanced Analysis Library Only
AnalysisLibErrType PolyFitEx (double arrayX[], double arrayY[], ssize_t numberOfElements, int order, int specCoefficientOrder[], double specCoefficients[], int numberOfSpecCoefficients, int algorithm, double fittedData[], double coefficients[], double *mse);
Purpose
Fits the data set (x, y) to a polynomial model using the Least Square method. The following equation represents the polynomial model:
where a0, a1, ... , am-1 are the polynomial coefficients.
Parameters
| Input | ||
| Name | Type | Description |
| arrayX | double [] | The x value of the data set (x, y). If fittedData is NULL, the best fit array overwrites arrayX. |
| arrayY | double [] | The y value of the data set (x, y). |
| numberOfElements | ssize_t | The length of arrayX and arrayY. |
| order | int | The order of the polynomial used in the polynomial fit operation. Polynomial order must be greater than or equal to 0. If the polynomial order is less than zero, this function sets the coefficients parameter to an empty array and returns an error. In real applications, polynomial order is less than 10. If the polynomial order is greater than 25, the function sets the coefficients beyond order 25 in the coefficients parameter to zero and returns a warning. |
| specCoefficientOrder | int [] | The orders on which the polynomial coefficients are constrained to be the known values specified in specCoefficients. Set specCoefficientOrder to NULL if there are no constrained coefficients. |
| specCoefficients | double [] | The coefficients on the orders specified in specCoefficientOrder. Set specCoefficients to NULL if there are no constrained coefficients. |
| numberOfSpecCoefficients | int | The length of specCoefficientOrder and specCoefficients. numberOfSpecCoefficients is optional. Set numberOfSpecCoefficients to 0 if a specified order and coefficients are not available. |
| algorithm | int | The algorithm used to solve the linear equations in polynomial fit. algorithm must be one of the following values. NI recommends that you use POLYFIT_SVD for numerical stability.
|
| Output | ||
| Name | Type | Description |
| fittedData | double [] | The y values calculated using the polynomial model. If fittedData is NULL, the best fit array overwrites arrayX. |
| coefficients | double [] | The coefficients of the fitted polynomial in ascending order of power. |
| MSE | double | The mean square error. |
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 8.0 and later