Group delay

Calculates and plots the group delay for an s domain system.

Description

Calculates and plots the group delay in a semilogx scale for a system created using tf. This includes to continuous time systems and s domain transfer functions.

For example
H = tf(1,[1 1]); %// 1st order low pass with cut off at 1 rad/sec
 groupDelaytf(H)
This will plot the group delay of the filter specified in H.

• Required Products: Control System Toolbox
• MATLAB release: MATLAB 7.3 (R2006b)

[Duane Hanselman]

Here is what is in this submission:
function groupDelay = groupDelaytf(SYS,varargin)
freqScale = 'rad/s';
if nargin > 2
    disp('Too many input arguments!');
    groupDelay = [];
    return
elseif nargin > 1
    freqScale = varargin{1};
end
sk = 2*pi;
if strcmp(freqScale,'Hz') || strcmp(freqScale,'hz')
    sk = 1;
end
[M,P,w] = bode(SYS);
w = linspace(w(1),w(end),length(w)*1000)/(sk);
[M,P] = bode(SYS,w*2*pi);
P = P(:)';
groupDelay = -gradient(P,w)/360;
grid on
semilogx(w*sk,groupDelay)
return