You can store the output of ‘freqs’ in a variable, say h. The following line of code would give you the magnitude in decibels:
mag = mag2db(abs(h));
For plotting the magnitude and phase response, you can use the ‘semilogx’ function which plots the x-axis in log scale and the y-axis in linear scale. You can find the code for that below:
h = freqs(b,a,w);
mag = mag2db(abs(h));
phase = angle(h);
phasedeg = phase*180/pi;
subplot(2,1,1), semilogx(w,mag), grid on
xlabel 'Frequency (rad/s)', ylabel Magnitude
subplot(2,1,2), semilogx(w,phasedeg), grid on
xlabel 'Frequency (rad/s)', ylabel 'Phase (degrees)'
For further capabilities of the ‘freqs’ function, refer to the examples in the following documentation:https://www.mathworks.com/help/signal/ref/freqs.html
