# IIRFiltering

Advanced Analysis Library Only

AnalysisLibErrType IIRFiltering (double xArray[], int numberXElements, double aCoefficientArray[], double yConditionsArray[], int numberACoefficients, double bCoefficientArray[], double xConditionsArray[], int numberBCoefficients, double yArray[]);

## Purpose

Filters the input sequence using the IIR filter specified by reverse coefficients aCoefficientArray and forward coefficients bCoefficientArray using the following formula:

The reverse and forward coefficients are obtained by respective IIR coefficient functions, such as Bw_Coef.

## Parameters

Input
Name | Type | Description
xArray | double-precision array | Array containing the raw data to filter.
numberXElements | integer | Number of points in both bCoefficientArray and xConditionsArray.
aCoefficientArray | double-precision array | Array that contains the reverse coefficients for the IIR filtering operation.
numberACoefficients | integer | Number of coefficients in both aCoefficientArray and yConditionsArray.
bCoefficientArray | double-precision array | Array that contains the forward coefficients for the IIR filtering operation.
numberBCoefficients | integer | Number of coefficients in both bCoefficientArray and xConditionsArray.
Output
Name | Type | Description
yConditionsArray | double-precision array | Array that contains the initial conditions, or states. The size of this array must be at least numberACoefficients — 1.
yConditionsArray | double-precision array | The final conditions for the next iterations.
xConditionsArray | double-precision array | Array that contains the initial conditions, or states. The size of this array must be at least bCoefficientArray — 1.
xConditionsArray | double-precision array | The final conditions for the next iterations.
yArray | double-precision array | The output of the IIR filtering operation. The size of this array must be at least numberXElements.

## 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.