MATLAB - Find Frequency of Transfer Function Corresponding to a Magnitude

Question

Given a transfer function H(s) , I plot the bode(H) . Now I want to get the frequency at which the magnitude equals a specific number.

Is this possible?

Answer 1

here's how to do this using find with the handles bode function gives you. Let's start with the following example:

H = tf([1 0.1 7.5],[1 0.12 9 0 0]);
[mag,phase,wout]=bode(H);

then use find as follows:

thr = 1e-2;
ind = find(mag>0.47-thr & mag<0.47+thr)

and the frequency for that magnitude (0.47) will be:

wout(ind)