problem in plotting data

Goodmorning,

I am doing a fit with a complex function: the code seems to work correctely but I cannot plot the data.

Do you have suggestion about what the problem is?

I attach the code I am working on and the data.

close all
clear 
clc
load 'f_B100_PEGNA_t30_bisSC.txt'
f_B100_PEGNA_t30_bisSC;
f=f_B100_PEGNA_t30_bisSC(:,1);
yR=f_B100_PEGNA_t30_bisSC(:,6);
yI=f_B100_PEGNA_t30_bisSC(:,7);

Y=yR-1i*yI;
DER=yR.*0.01;
DEI=yI.*0.01;
DE_tot=DER+1i*DEI;
weightR=1./DER;
weightI=1./DEI;
weightT=1./DE_tot;


fit_fun=@(r,f) abs(r(1))+abs(r(2))./(1+(1i*f*2*pi*r(3)).^(abs(1-abs(r(4))))).^(r(5));
fit_funw=@(r) norm(weightR.*real(fit_fun(r,f)-Y)+1j*weightI.*imag(fit_fun(r,f)-Y));
r0=[1,1,1,1,1];
r=fminsearch(fit_funw,r0);

 
Exiting: Maximum number of function evaluations has been exceeded
         - increase MaxFunEvals option.
         Current function value: 902.572770 

r=r(:)

r = 5×1

3.5956 2.7170 -0.0000 1.1588 -2.0959

figure(1)
loglog(f,yR,'o',f,real(fit_fun(r,f)))

figure(2)
loglog(f,yI,'o',f,-imag(fit_funw(r)))

Thank you all!

Answer 1

[Cris LaPierre]

I changed your post to executable code and ran in here. Two plots were created. Are those the figures you are trying to create? I suspect you expect to see a line in the second plot?

Upon inspection, the result of fit_funw(r) is a single number, 902.5728. It is not a complex number, so the result of imag is 0.

By default, the plot function does not include a markerstyle. It just plots using a solid line. When you data is a single point, you cannot see that line. This is because norm returns a single value for a vector input. Specify a marker style for the second plot.

If you expect fit_funw to return a vector, please check your approach.

[Daniele Sonaglioni]

Thank you @Cris LaPierre but I was experiencing a problem with Matlab and the plots were not visible. Anyway, I have subsequently improved the code with GlobalSearch.

Referring to the question above, the code was right, the only problem was with Matlab but now I have solved everything. If you can, I wuold ask if can delete the question because it is not useful for other users at all.

Thank you!