Finding frequencies corresponding to some gain on Band Pass Filter Bode Plot

Good evening,

I'm trying to use this code to find specific frequencies on a band pass filter bode plot, given the gain value, but since I have 2 frequencies for each gain value, I'm getting errors saying that the sample points from the bode plot must be in ascending order.

I can do it the other way (find gain given the frequency), but is there a way for me to get the 2 frequencies for a given gain value?

Thanks.

wo = 2*pi*120;
Bw = 2*pi*12;

num=[Bw 0];
den=[1 Bw wo^2];

sys=tf(num, den)
bode(sys)

[mag, phase, wout]=bode(sys);

mag=squeeze(mag);
phase=squeeze(phase);

MaxGain = max(20*log10(mag))

Gain120hz = interp1(wout, 20*log10(mag), wo)

w0 = interp1(20*log10(mag), wout, MaxGain)

Answer 1

[Mathieu NOE]

wo = 2*pi*120;
Bw = 2*pi*12;
num=[0 Bw 0];
den=[1 Bw wo^2];
w = logspace(log10(wo/2),log10(wo*2),400);  % w vector log and symetrical around 120 Hz
sys=tf(num, den)
bode(sys,w)
[mag, phase, wout]=bode(num,den,w);
% mag=squeeze(mag);
% phase=squeeze(phase);

[MaxGain,ind] = max(20*log10(mag));
MaxGain
w0 = wout(ind);
f0 = w0/2/pi

Gain120hz = interp1(wout, 20*log10(mag), wo)

% w0 = interp1(20*log10(mag), wout, MaxGain); % no : X vector may not be
% uniform