CascadeToDirectCoef
Advanced Analysis Library Only
AnalysisLibErrType CascadeToDirectCoef (IIRFilterPtr filterInformation, double aCoefficientArray[], int numberOfACoefficients, double bCoefficientArray[], int numberOfBCoefficients);
Purpose
Converts from the cascade IIR coefficients contained by the filterInformation structure to direct-form IIR coefficients in arrays aCoefficientArray and bCoefficientArray. These two arrays must be allocated in the same way as the old-style direct coefficient design functions, for example, Bw_Coef.
To redesign another filter, first call FreeIIRFilterPtr to free the present filter structure and then call AllocIIRFilterPtr with the new type and order parameters before you call CascadeToDirectCoef.
For lowpass and highpass type filters, the direct coefficient arrays must equal (order + 1).
For bandpass and bandstop type filters, the direct coefficient arrays must equal (2 × order + 1).
Parameters
| Input | ||
| Name | Type | Description |
| filterInformation | IIRFilterPtr | Pointer to the filter structure that contains the filter coefficients and the internal filter information. You must allocate this structure by calling AllocIIRFilterPtr before calling one of the cascade IIR filter design functions. |
| numberOfACoefficients | int | The number of coefficients in aCoefficientArray. numberACoefficients = order + 1 for low- or highpass filters numberACoefficients = 2 × order + 1 for bandpass or bandstop filters |
| numberOfBCoefficients | int | The number of coefficients in bCoefficientArray. numberBCoefficients = order + 1 for low- or highpass filters numberBCoefficients = 2 × order + 1 for bandpass or bandstop filters |
| Output | ||
| Name | Type | Description |
| aCoefficientArray | double [] | Array that contains the reverse coefficients of the direct-form IIR filter. |
| bCoefficientArray | double [] | Array that contains the forward coefficients of the direct-form IIR filter. |
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 4.0 and later