Last Modified: January 12, 2018

Filters an input sequence using a specific filter.

You can specify the initial conditions for this node.

A Boolean that specifies the initialization of the internal state of the node.

True | Initializes the internal state to the value of condition in if condition in is wired or to zero if condition in is unwired. |

False | Sets the internal state to the final state from the previous call of this node. |

**Default: **False

Input signal to filter.

This input accepts the following data types:

- Waveform
- Double-precision, floating-point number
- Complex double-precision, floating-point number
- Waveform in complex double-precision, floating-point numbers
- 1D array of waveforms
- 1D array of double-precision, floating-point numbers
- 1D array of complex double-precision, floating-point numbers
- 1D array of waveforms in complex double-precision, floating-point numbers
- 2D array of double-precision, floating-point numbers

Input filter.

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. |

**Default: **IIR Cascade 2nd Order

Forward coefficients of the filter.

Reverse coefficients of the filter.

Sampling frequency in Hz.

This input must be greater than 0.

Initial internal state of the filter.

Values of the initial internal state of the filter.

Error conditions that occur before this node runs.

The node responds to this input according to standard error behavior.

Standard Error Behavior

Many nodes provide an **error in** input and an **error out** output so that the node can respond to and communicate errors that occur while code is running. The value of **error in** specifies whether an error occurred before the node runs. Most nodes respond to values of **error in** in a standard, predictable way.

**Default: **No error

Filtered signal.

This output can return the following data types:

- Waveform
- Double-precision, floating-point number
- Complex double-precision, floating-point number
- Waveform in complex double-precision, floating-point numbers
- 1D array of waveforms
- 1D array of double-precision, floating-point numbers
- 1D array of complex double-precision, floating-point numbers
- 1D array of waveforms in complex double-precision, floating-point numbers
- 2D array of double-precision, floating-point numbers

Final internal state of the filter.

Values of the final internal state of the filter.

Error information.

The node produces this output according to standard error behavior.

Standard Error Behavior

**error in** input and an **error out** output so that the node can respond to and communicate errors that occur while code is running. The value of **error in** specifies whether an error occurred before the node runs. Most nodes respond to values of **error in** in a standard, predictable way.

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

${y}_{i}=\begin{array}{cc}\underset{j=0}{\overset{{N}_{b}-1}{\sum}}{b}_{j}{x}_{i-j}& \mathrm{for}(i\ge 0)\end{array}$

where

*y*is**filtered signal***N*_{b}is the number of FIR coefficients*b*_{j}is the filter coefficients

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

${y}_{i}=\begin{array}{cc}\frac{1}{{a}_{0}}\left(\underset{j=0}{\overset{{N}_{b}-1}{\sum}}{b}_{j}{x}_{i-j}-\underset{k=1}{\overset{{N}_{a}-1}{\sum}}{a}_{k}{y}_{i-k}\right)& \mathrm{for}(i\ge 0)\end{array}$

where

*y*is**filtered signal***N*_{b}is the number of**forward coefficients***b*_{j}is the**forward coefficients***N*_{a}is the number of**reverse coefficients***a*_{k}is the**reverse coefficients**

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 *N*_{s} filter stages.

**Where This Node Can Run: **

Desktop OS: Windows

FPGA: Not supported

Web Server: Not supported in VIs that run in a web application