## Documentation Center |

2-D frequency response

`[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(...)`

`[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.

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`.

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])

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