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########################################################################
##
## Copyright (C) 2002-2024 The Octave Project Developers
##
## See the file COPYRIGHT.md in the top-level directory of this
## distribution or <https://octave.org/copyright/>.
##
## This file is part of Octave.
##
## Octave is free software: you can redistribute it and/or modify it
## under the terms of the GNU General Public License as published by
## the Free Software Foundation, either version 3 of the License, or
## (at your option) any later version.
##
## Octave is distributed in the hope that it will be useful, but
## WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
## GNU General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with Octave; see the file COPYING. If not, see
## <https://www.gnu.org/licenses/>.
##
########################################################################
## -*- texinfo -*-
## @deftypefn {} {} freqz_plot (@var{w}, @var{h})
## @deftypefnx {} {} freqz_plot (@var{w}, @var{h}, @var{freq_norm})
## Plot the magnitude and phase response of @var{h}.
##
## If the optional @var{freq_norm} argument is true, the frequency vector
## @var{w} is in units of normalized radians. If @var{freq_norm} is false, or
## not given, then @var{w} is measured in Hertz.
## @seealso{freqz}
## @end deftypefn
function freqz_plot (w, h, freq_norm = false)
if (nargin < 2)
print_usage ();
endif
n = length (w);
## ## exclude zero-frequency
## h = h (2 : length (h));
## w = w (2 : length (w));
## n = n-1;
mag = 20 * log10 (abs (h));
phase = unwrap (arg (h));
if (freq_norm)
x_label = 'Normalized Frequency (\times\pi rad/sample)';
else
x_label = "Frequency (Hz)";
endif
subplot (2, 1, 1);
plot (w, mag);
grid ("on");
axis ([w(1), w(n)], "autoy");
xlabel (x_label);
ylabel ("Magnitude (dB)");
subplot (2, 1, 2);
plot (w, phase*360/(2*pi));
grid ("on");
axis ([w(1), w(n)], "autoy");
xlabel (x_label);
ylabel ("Phase (degrees)");
endfunction
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