DifferenceEx
Advanced Analysis Library Only
AnalysisLibErrType DifferenceEx (double inputArray[], ssize_t numberOfElements, double samplingInterval, double initialConditions[], ssize_t initialConditionsSize, double finalConditions[], ssize_t finalConditionsSize, int differenceMethod, double outputArray[]);
Purpose
Differentiates the input signal inputArray using the second order central, fourth order central, forward, or backward differentiation method.
If differenceMethod is SECOND_ORDER_CENTRAL_DIFF, outputArray is given by
for i = 0,1,2,...,n-1 where n is the length of inputArray, x_{-1} is the first element in initialConditions, and x_{n} is the first element in finalConditions.
If differenceMethod is FOURTH_ORDER_CENTRAL_DIFF, outputArray is given by
for i = 0,1,2,...,n-1
where n is the length of inputArray, x_{-2} and x_{-1} are the first and second elements in initialConditions, x_{n} and x_{n+1}are the first and second elements in final condition.
If differenceMethod is FORWARD_DIFF, outputArray is given by
for i = 0,1,2,...,n-1
where n is the length of inputArray, x_{n} is the first element in finalConditions.
If differenceMethod is BACKWARD_DIFF, outputArray is given by:
for i = 0,1,2,...,n-1
where n is the length of inputArray, x_{-1} is the first element of initialConditions.
Parameters
| Input | ||
| Name | Type | Description |
| numberOfElements | ssize_t | The length of inputArray. |
| samplingInterval | double | The sampling interval. samplingInterval must be greater than zero. |
| initialConditions | double [] | The initial condition array of inputArray. The function uses the first element in initialConditions to calculate the derivative if differenceMethod is SECOND_ORDER_CENTRAL_DIFF or BACKWARD_DIFF. The function uses the first two elements in initialConditions to calculate the derivative if differenceMethod is FOURTH_ORDER_CENTRAL_DIFF. |
| initialConditionsSize | ssize_t | The length of initialConditions. If differenceMethod is SECOND_ORDER_CENTRAL_DIFF or BACKWARD_DIFF, initialConditionsSize must be 1. If differenceMethod is FOURTH_ORDER_CENTRAL_DIFF, initialConditionsSize must be 2. |
| finalConditions | double [] | The final condition array of inputArray. The function uses the first element in finalConditions to calculate the derivative if differenceMethod is SECOND_ORDER_CENTRAL_DIFF or FORWARD_DIFF. The function uses the first two elements in finalConditions to calculate the derivative if method is FOURTH_ORDER_CENTRAL_DIFF. |
| finalConditionsSize | ssize_t | The length of finalConditions. If differenceMethod is SECOND_ORDER_CENTRAL_DIFF or FORWARD_DIFF, finalConditionsSize must be 1. If differenceMethod is FOURTH_ORDER_CENTRAL_DIFF, finalConditionsSize must be 2. |
| differenceMethod | int | The differentiation method. differenceMethod must be one of the following values:
|
| Output | ||
| Name | Type | Description |
| inputArray | double [] | The sampled signal to perform differentiation. If outputArray is NULL, the differentiation result overwrites inputArray. |
| outputArray | double [] | The differentiation of inputArray. |
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 8.5 and later