# This code shows the FIR filter magnitude response with the normalized frequency from 0 to pi, how i can make mirroring of this magnitude response to start from -pi to pi ??

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Aly Khafagy on 7 May 2022
Answered: Mathieu NOE on 9 May 2022
This code shows the FIR filter magnitude response with the normalized frequency through interval from [0 to pi] in a figure, my question is how i can make mirroring of this magnitude response to start through interval from [-pi to pi] ??
clc;
close all;
clear all;
n1= 15; %order
Fs= 100; %sampling frequency
fc= Fs/4; %cutoff frequency
%nyq_f= Fs/2; %normalize cutoff frequency wrt to nyquist freq
%wn= fc/nyq_f; %normalized fc
wc= (2*pi*fc)/Fs;
wn= wc/pi;
%window= hamming(n+1)
H1= fir1(n1,wn,hamming(n1+1));
h1= freqz(H1); %frequency response
f1= linspace(0,Fs/2,512);
w1= (2*pi*f1)/Fs;
w= w1/pi;
plot (w, abs(h1))
axis([0 1 -0.1 1.1])

Mathieu NOE on 9 May 2022
hello
here you are (nothing fancy !)
clc;
close all;
clear all;
n1= 15; %order
Fs= 100; %sampling frequency
fc= Fs/4; %cutoff frequency
%nyq_f= Fs/2; %normalize cutoff frequency wrt to nyquist freq
%wn= fc/nyq_f; %normalized fc
wc= (2*pi*fc)/Fs;
wn= wc/pi;
%window= hamming(n+1)
H1= fir1(n1,wn,hamming(n1+1));
h1= freqz(H1); %frequency response
f1= linspace(0,Fs/2,512);
w1= (2*pi*f1)/Fs;
w= w1/pi;
h1_mag = abs(h1);
plot (w, h1_mag)
axis([0 1 -0.1 1.1])
% This code shows the FIR filter magnitude response with the normalized frequency through interval from [0 to pi] in a figure,
% my question is how i can make mirroring of this magnitude response to start through interval from [-pi to pi] ??
w_flip = flip(w);
h1_mag_flip = flip(h1_mag);
w_all = [-w_flip(1:end-1) w];
h1_mag_all = [h1_mag_flip(1:end-1); h1_mag];
plot (w_all, h1_mag_all)
axis([-1 1 -0.1 1.1])