MATLAB: How to make fft2 surf plot with z axis in dB

dbdecibelsMATLAB

i tried to normalize this matrix with the maximum

and: p=10*log10(p);

but i get mess

how can i avoid that?

Best Answer

Without access to your data, it’s difficult to say. Two possibilities:

First:

p = 10*log10(abs(p));

Second:

p = 10*log10(abs(p)+1E-2);

Related Solutions

MATLAB: Visualise fft plot in 3D

Use the ribbon (link) plot.

The Code —

d = load('Athira Surendran sjs1.mat');
amp = d.amp';                                           % Amplitude (Transposed)
load = d.load;                                          % Load
t = d.t;                                                % Time
Ts = mean(diff(t));                                     % Sampling Interval
Fs = 1/Ts;                                              % Sampling Frequency
Fn = Fs/2;                                              % Nyquist Frequency
L = length(t);
FTamp = fft(amp)/L;                                     % Fourier Transform
Fv = linspace(0, 1, fix(L/2)+1)*Fn;                     % Frequency Vector
Iv = 1:length(Fv);                                      % Index Vector
figure(1)
hr = ribbon(Fv, abs(FTamp(Iv,:))*2, 0.1);
grid on
for k1 = 1:length(hr)
    set(hr(k1), 'FaceColor','b', 'EdgeColor','b')
    xpos = get(hr(k1), 'XData');
    xtix(k1) = mean(xpos(1,:));
end
set(gca, 'XTick',xtix, 'XTickLabel',load)
xlabel('Load')
ylabel('Frequency (Hz)')
zlabel('Amplitude')
view([135,  30])

I believe that I chose the correct variables. If not, changing my code to use the correct ones is straightforward.

The Plot —

MATLAB: Failure in initial objective function evaluation. FMINCON cannot continue.

You have 17 unknowns but the initial guess that you passed to fmincon is a scalar.

Best Answer

Related Solutions

MATLAB: Visualise fft plot in 3D

MATLAB: Failure in initial objective function evaluation. FMINCON cannot continue.

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