smoothing a graph using matlab
3 views (last 30 days)
Show older comments
Abeer Aboul Azm
on 20 Feb 2022
Commented: Star Strider
on 20 Feb 2022
how can I smooth data imported from one column (Excel sheet) using Matlab
how to smooth the corners?
0 Comments
Accepted Answer
Star Strider
on 20 Feb 2022
A frequency-selective filter can preseerve the essential shape of the signal, eliminating only the high-frequency oscillations in the ‘valleys’.
Try this —
V1 = readmatrix('https://www.mathworks.com/matlabcentral/answers/uploaded_files/900720/data.xlsx');
L = numel(V1);
t = linspace(0, L-1, L);
Ts = t(2)-t(1);
Fs = 1/Ts;
Fn = Fs/2;
NFFT = 2^nextpow2(L);
FTV1 = fft(V1,NFFT);
Fv = linspace(0, 1, NFFT/2+1)*Fn;
Iv = 1:numel(Fv);
figure
plot(Fv, abs(FTV1(Iv))*2)
grid
xlabel('Frequency')
ylabel('Amplitude')
title('Fourier Transform (Detail)')
xlim([0 0.05])
UpperPassband = 0.023;
V1F = lowpass(V1, UpperPassband, Fs, 'ImpulseResponse','iir');
figure
subplot(2,1,1)
plot(t, V1)
grid
title('Original')
subplot(2,1,2)
plot(t, V1F)
grid
xlabel('Time')
title('Filtered')
Adjust the ‘UpperPassband’ frequency to produce the desired result.
.
2 Comments
Image Analyst
on 20 Feb 2022
This looks like it maintains the shape of the "good" part better than the Savistky-Golay filter.
Star Strider
on 20 Feb 2022
I like the sgolayfilt function and use it to filter broadband noise. However, this is band-limited noise (the reason I did the fft was to determine that) so a frequency-selective filter works best in this instance.
More Answers (1)
Image Analyst
on 20 Feb 2022
You could use sgolayfilt() to fit a sliding window to the data. Window width would be about the width of one of those humps. It looks kind of like a sine or cosine wave thus you can fit it to a 4th or 5th order polynomial. Attach your data if you need more help.
6 Comments
Image Analyst
on 20 Feb 2022
Edited: Image Analyst
on 20 Feb 2022
If it worked, can you click "Accept this answer" for the best answer? Thanks in advance.
See Also
Products
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!