data to transfer function (idfrd) error

data = importdata ('C:\Users\sangwoo\Desktop\mash_change_500Hz_tf.mat');
freq = 1:1:500;   % frequency range
w = freq*2*pi; %angle freq
frf = data;   % FRF complex number 

Fs = 500*2*32;
Ts = 1/Fs;

np = 10; %number of poles
nz = 10; %number of zeros

%% 1 iddata 
gfr = idfrd(frf,w,Ts) 

%% 2 system 

sys = tfest(gfr,np,nz)

%% 3 num, den 

num = sys.Numerator;
den = sys.Denominator;
% 
% %% 4 continuous transfer function
% 
G = tf([num],[den]);
figure(1)
bode(G)
figure(2)
semilogx(2*pi*freq,20*log10(abs(frf))) %compare 

left is plot from data right is plot of G ; rad/s and magnitude at resonance is not matched

at tfest process, matlab tell accuracy is 99.7 percent. so i think gfr = tfest. but at idfrd process, some bad think happened. please give me some help to make accurate model

[sangwoo ha]

sorry i have no idea about iddata i think gfr is perfect but something wrong in tfest

Answer 1

[Star Strider]

If you want to see how well the data and identified system match, use the compare function.