how to plot the frequency response of low pass filter in matlab in matlab

To plot the frequency response of a low pass filter in MATLAB, follow the steps below:

1. Define the filter coefficients using appropriate filter design functions, such as butter, cheby1, or ellip. For example, to design a low pass Butterworth filter of order 4 with normalized cut-off frequency of 0.2, use the following command:

main.m
[b, a] = butter(4, 0.2);
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2. Use the freqz function to compute and plot the frequency response of the filter. The freqz function takes the filter coefficients as inputs and returns the complex frequency response and the frequency vector. To plot the magnitude response of the filter, use the abs function on the frequency response, and to plot the phase response, use the angle function. For example, to plot the magnitude and phase responses of the filter, use the following commands:

main.m
[H, w] = freqz(b, a);
subplot(2, 1, 1);
plot(w/pi, abs(H));
title('Magnitude Response');
xlabel('Normalized Frequency (\times\pi rad/sample)');
ylabel('|H(\omega)|');
subplot(2, 1, 2);
plot(w/pi, angle(H));
title('Phase Response');
xlabel('Normalized Frequency (\times\pi rad/sample)');
ylabel('\angleH(\omega)');
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This will result in a plot with the magnitude and phase responses of the low pass filter.