How to smooth a curve in Matlab?

Hi;

I have graphic. But in the graphic, there are a few spikes as it is seen in the attached jpg file. They are showed in black circle. How can I plot the graphic by excluding these spikes? I mean; how can I plot a smooth curve?

I also attach .txt file..

Regards,

Answer 1

[Star Strider]

This will filter out most of the noise. I could not filter out more of it without filtering out parts of your signal.

The Code —

d = load('test1.txt');
d1 = d(:,1);                                                    % Original Time Vector
d2 = d(:,2);                                                    % Original Data Vector
L = length(d1);
tv = linspace(min(d1), max(d1), L);                             % Time Vector For Interpolation
dv = interp1(d1, d2, tv, 'linear');                             % Interpolated Data Vector

Ts = mean(diff(tv));                                            % Sampling Time Interval
t_stats = [Ts  std(tv)];
Fs = 1/Ts;                                                      % Sampling Frequency
Fn = Fs/2;                                                      % Nyquist Frequency

FTD = fft(dv)/L;                                                % Fourier Transform
Fv = linspace(0, 1, fix(L/2)+1)*Fn;                             % Frequency Vector
Iv = 1:length(Fv);                                              % Index Vector

figure(1)
semilogy(Fv, abs(FTD(Iv))*2)                                    % Plot Fourier Transform
grid
xlabel('Frequency (Hz)')
ylabel('Amplitude')

Wp = 3/Fn;                                                      % Low Pass Filter Passband
Ws = 4/Fn;                                                      % Low Pass Filter Stopband
Rp=10;                                                          % Low Pass Filter Passband Ripple
Rs=30;                                                          % Low Pass Filter Stopband Ripple
[n,Ws] = cheb2ord(Wp,Ws,Rp,Rs);                                 % Design Chebyshev Type II Filter
[z,p,k] = cheby2(n,Rs,Ws);
[sos,g] = zp2sos(z,p,k);                                        % Second Order Section For Stability

figure(2)
freqz(sos, 2^16, Fs)                                            % Filter Bode Plot
set(subplot(2,1,1), 'XLim',[0 100])                             % ‘Zoom’ X-Axis
set(subplot(2,1,2), 'XLim',[0 100])                             % ‘Zoom’ X-Axis

dv_filt = filtfilt(sos, g, dv);                                 % Filter Data

figure(3)
plot(d(:,1), d(:,2))
hold on
plot(tv, dv_filt, 'LineWidth',1)
hold off
grid
xlabel('Time (s)')
ylabel('Amplitude')
legend('Original Signal', 'Filtered Signal')