# freqz2

2-D frequency response

## Syntax

[H, f1, f2] = freqz2(h, n1, n2)
[H, f1, f2] = freqz2(h, [n2 n1])
[H, f1, f2] = freqz2(h)
[H, f1, f2] = freqz2(h, f1, f2)
[...] = freqz2(h,...,[dx dy])
[...] = freqz2(h,...,dx)
freqz2(...)

## Description

[H, f1, f2] = freqz2(h, n1, n2) returns H, the n2-by-n1 frequency response of h, and the frequency vectors f1 (of length n1) and f2 (of length n2). h is a two-dimensional FIR filter, in the form of a computational molecule. f1 and f2 are returned as normalized frequencies in the range -1.0 to 1.0, where 1.0 corresponds to half the sampling frequency, or π radians.

[H, f1, f2] = freqz2(h, [n2 n1]) returns the same result returned by [H,f1,f2] = freqz2(h,n1,n2).

[H, f1, f2] = freqz2(h) uses [n2 n1] = [64 64].

[H, f1, f2] = freqz2(h, f1, f2) returns the frequency response for the FIR filter h at frequency values in f1 and f2. These frequency values must be in the range -1.0 to 1.0, where 1.0 corresponds to half the sampling frequency, or π radians.

[...] = freqz2(h,...,[dx dy]) uses [dx dy] to override the intersample spacing in h. dx determines the spacing for the x dimension and dy determines the spacing for the y dimension. The default spacing is 0.5, which corresponds to a sampling frequency of 2.0.

[...] = freqz2(h,...,dx) uses dx to determine the intersample spacing in both dimensions.

freqz2(...)produces a mesh plot of the two-dimensional magnitude frequency response when no output arguments are specified.

## Class Support

The input matrix h can be of class double or of any integer class. All other inputs to freqz2 must be of class double. All outputs are of class double.

## Examples

Use the window method to create a 16-by-16 filter, then view its frequency response using freqz2.

Hd = zeros(16,16);
Hd(5:12,5:12) = 1;
Hd(7:10,7:10) = 0;
h = fwind1(Hd,bartlett(16));
colormap(jet(64))
freqz2(h,[32 32]); axis ([-1 1 -1 1 0 1])