MATLAB: Bode Plot data extraction to xlsx file format

Question

The coefficinets a1,a2, b1, b2 k1, k2 are computed using some arithmetic calculations according to some specific requirement. After the computation Bode plot is done for High pass, Notch and Low pass filters. The requirement for me is to obtain the data of the bode plot (corresponding magnitude vs frequency and phase vs freq) in to a csv file or text file.

Bode plot respons is as expected and the problem I am facing for the

xlswrite('data.xlsx', [dat1,dat2,dat3]) command is Input data must be a numeric, cell, or logical array.

Even in the Data Statistics tab the values are displaying as NaN

Can somebody suggest a solution or workaround ?

Code:

%HighPass Filter

Vin=[1 a1 a0];

V01=[0 ((-(k2*b2*a1))+(k2*b1)) ((-k2*b2*a0)+(k2*b0))];

LP=tf(V01,Vin)

opts = bodeoptions;

opts.FreqUnits = 'kHz';

dat1=bodeplot(LP,opts,'r');

hold on

%Notch Filter

Vin=[1,a1,a0];

V02=[b2,b1,b0];

HP=tf(V02,Vin)

opts = bodeoptions;

opts.FreqUnits = 'kHz';

dat2=bodeplot(HP,opts,'b');

hold on

%Low Pass Filter

Vin=[(K1*sqrt(a0)) (a1*(K1*sqrt(a0))) (a0*(K1*sqrt(a0)))];

V03=[0 ((b0-(b2*a0))) ((a1*b0)-(a0*b1))];

BN=tf(V03,Vin)

opts = bodeoptions;

opts.FreqUnits = 'kHz';

dat3=bodeplot(BN,opts,'g');

hold off

Answer 1

It is essentially impossible to get any useful results from bodeplot. It is intended to provide plot options.

Use the bode function instead:

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

You will have to transform the radian frequencies in ‘wout’ to Hz:

fHz = wout/(2*pi);