%% Sigma Plot at Specified Frequencies
% Create a singular value plot over a specified frequency range. Use this approach when you want to focus on the dynamics in a particular range of frequencies.

H = tf([-0.1,-2.4,-181,-1950],[1,3.3,990,2600]);
sigma(H,{1,100})
grid on

% The cell array {1,100} specifies the minimum and maximum frequency values in the plot. When you provide frequency bounds in this way, the function selects intermediate points for frequency response data.
% Alternatively, specify a vector of frequency points to use for evaluating and plotting the frequency response.

w = [1 5 10 15 20 23 31 40 44 50 85 100];
sigma(H,w,'.-')
grid on

% sigma plots the frequency response at the specified frequencies only.
% Copyright 2021 The MathWorks, Inc.