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Member of the filter design class.

Syntax

freqz(b)

freqz(b, a)

freqz(b, a, w)

freqz(b, a, w, fs)

freqz(b, a, n)

freqz(b, a, n, 'whole')

freqz(b, a, n, fs)

freqz(b, a, n, 'whole', fs)

h = freqz(b, a, w)

h = freqz(b, a, w, fs)

[h, f] = freqz(b)

[h, f] = freqz(b, a)

[h, f] = freqz(b, a, n)

[h, f] = freqz(b, a, n, 'whole')

[h, f] = freqz(b, a, n, fs)

[h, f] = freqz(b, a, n, 'whole', fs)

Description

Computes the complex frequency response vector and the frequency vector of a filter. If you do not request an output, this function plots the magnitude and unwrapped phase of the filter in the current plot window. freqz(b) is equivalent to freqz(b, [1], 512). freqz(b, a) is equivalent to freqz(b, a, 512).

Details

Examples

Inputs

Name	Description
b	Specifies the numerator coefficients of the filter. b is a real or complex vector.
a	Specifies the denominator coefficients of the filter. a is a real or complex vector. The default is [1].
w	Specifies the frequency points at which you want to evaluate the frequency response. If you do not specify w, LabVIEW evaluates the frequency response at n points equally spaced around the upper half of the unit circle. w is a vector.
fs	Specifies the sampling frequency in Hz. fs is a scalar.
n	Specifies the number of frequency points. n is a positive integer. The default is 512.
'whole'	Directs LabVIEW to evaluate the frequency response at n points equally spaced around the unit circle.

Outputs

Name	Description
h	Returns the frequency response vector of the filter. h is a complex vector.
f	Returns the discrete frequency vector in radians/sample that corresponds to h. f is a vector.

Details

This function is supported in the LabVIEW Run-Time Engine only if you request an output from the function. This function can remain in your scripts when you build a stand-alone application or shared library, but if you do not request an output, the LabVIEW Run-Time Engine does not execute this function. If you request an output, the LabVIEW Run-Time Engine executes this function as normal.

Examples

b = [1, 2];
a = [-1, 1, 1, 3];
n = 32;
[H, F] = freqz(b, a, n)

b = [3, 4];
a = [1, -3, 2, 5];
n = 10;
fs = 12;
[H, F] = freqz(b, a, n, 'whole', fs)

Related Topics

freqs
freqspace
grpdelay
impz
invfreqz
stepz