# Filtering (With Initial Conditions) (G Dataflow)

Version:

Filters an input sequence using a specific filter. You specify the initial conditions for this node.

## signal

Input signal to filter.

This input can be an array of double-precision floating-point numbers or an array of complex double-precision floating-point numbers.

## filter

The input filter.

### filter structure

Structure of the filter.

Name Value Description
IIR Cascade 2nd Order 0 Uses IIR second-order filter stages.
IIR Cascade 4th Order 1 Uses IIR fourth-order filter stages.
IIR Direct 2 Uses the direct-form IIR filter.
FIR 3 Uses the FIR filter.

### forward coefficients

Forward coefficients of the filter.

Default: 0

### reverse coefficients

Reverse coefficients of the filter.

Default: 0

### sampling frequency

The sampling frequency in Hz.

This value must be greater than zero.

Default: 0

## initial conditions

The initial internal filter state. This input must be passed from the final conditions output of the previous call to this node to filter samples continuously.

### condition

Values of the initial internal filter state.

## error in

Error conditions that occur before this node runs. The node responds to this input according to standard error behavior.

Default: No error

## filtered signal

The filtered signal.

## final conditions

The final internal filter state. You can pass this output to the initial conditions input of the next call to this node to filter samples continuously.

### condition

Values of the final internal filter state.

## error out

Error information. The node produces this output according to standard error behavior.

## Algorithm for Obtaining Filtered Signal with the FIR Filter

If filter structure is FIR, this node obtains the elements of filtered signal using the following equation:

${y}_{i}=\begin{array}{cc}\underset{j=0}{\overset{{N}_{b}-1}{\sum }}{b}_{j}{x}_{i-j}& \mathrm{for}\left(i\ge 0\right)\end{array}$
where
• y is filtered signal
• Nb is the number of FIR coefficients
• bj is the filter coefficients

## Algorithm for Obtaining Filtered Signal with the IIR Filter

If filter structure is IIR Direct, this node obtains the elements of filtered signal using the following equation:

${y}_{i}=\begin{array}{cc}\frac{1}{{a}_{0}}\left(\underset{j=0}{\overset{{N}_{b}-1}{\sum }}{b}_{j}{x}_{i-j}-\underset{k=1}{\overset{{N}_{a}-1}{\sum }}{a}_{k}{y}_{i-k}\right)& \mathrm{for}\left(i\ge 0\right)\end{array}$
where
• y is filtered signal
• Nb is the number of forward coefficients
• bj is the forward coefficients
• Na is the number of reverse coefficients
• ak is the reverse coefficients

## Algorithm for Obtaining Filtered Signal with the IIR Cascade Filter

If filter structure is IIR Cascade 2nd Order or IIR Cascade 4th Order, this node obtains the elements of filtered signal with a cascade of second- or fourth-order filter stages. The output of one filter stage is the input to the next filter stage for all Ns filter stages.

Where This Node Can Run:

Desktop OS: Windows

FPGA: Not supported