# freqz

Frequency response of discrete-time filter

## Syntax

## Description

`[`

returns the complex frequency response of the specified filter and the corresponding
frequencies at `filtresp`

,`w`

]
= freqz(`rcfilter`

,`n`

)`n`

points that are equally spaced around the upper-half
of the unit circle (from 0 to π).

This function uses the transfer function that is associated with the specified filter to calculate the frequency response of the filter with the current coefficient values.

## Examples

## Input Arguments

## Output Arguments

## Tips

Several ways exist for analyzing the frequency response of filters. The

`freqz`

function accounts for quantization effects in the filter coefficients but does not account for quantization effects in filtering arithmetic. To account for the quantization effects in filtering arithmetic, see the`noisepsd`

function.For faster computations (performed using FFTs), specify

`n`

, the number of points over which the function computes the frequency response, as a power of two.

## Algorithms

The `freqz`

function calculates the frequency response for a filter
from the filter transfer function *Hq*(*z*). The
complex-valued frequency response is calculated by evaluating
*Hq*(*e ^{j}^{ω}*)
at discrete values of

`w`

. The input
argument `n`

specifies the
number of equally-spaced points around the upper-half of the unit circle at which the function
evaluates the frequency response. When you do not specify scalar sampling frequency

`fs`

as an input argument, the frequency ranges from 0 to π radians per sample.When you specify scalar sampling frequency

`fs`

as an input argument to`freqz`

, the frequency ranges from 0 to`fs`

/2 Hz. For more information about`fs`

, see the`freqz`

function.

## Version History

**Introduced in R2013b**