How can i found the infelction point from the data and remove the data before the first and last infelction points.
1 vue (au cours des 30 derniers jours)
Afficher commentaires plus anciens
I need to find the inflection point from the experimental data using matlab. Kindly help me for that. Thanks in advance
0 commentaires
Réponses (2)
Star Strider
le 16 Jan 2023
The data are quite noisy. After filtering them, it is not obvious what sort of inflection point you want or how to define it.
M1 = readmatrix('https://www.mathworks.com/matlabcentral/answers/uploaded_files/1265285/data.xlsx')
x = M1(:,1);
y = M1(:,2);
% yf = sgolayfilt(y, 3, 451);
Fs = 1/mean(diff(x))
Fn = Fs/2;
L = numel(x);
NFFT = 2^nextpow2(L);
FTy = fft((y-mean(y)).*hann(L),NFFT)/L;
Fv = linspace(0, 1, NFFT/2+1)*Fn;
Iv = 1:numel(Fv);
figure
semilogy(Fv, abs(FTy(Iv))*2)
grid
xlim([0 10])
yf = lowpass(y, 0.5, Fs, 'ImpulseResponse','iir');
dyfdx = gradient(yf) ./ gradient(x);
d2yfdx2 = gradient(dyfdx) ./ gradient(x);
figure
yyaxis left
plot(x, y, 'DisplayName','Unfiltered Data')
hold on
plot(x, yf, '-r', 'DisplayName','Filtered Data')
hold off
ylabel('Data')
yyaxis right
plot(x, dyfdx, 'DisplayName','First Derivative Of Filtered Data')
hold on
plot(x, d2yfdx2, 'DisplayName','Second Derivative Of Filtered Data')
hold off
yline(0, '-g')
ylabel('Derivatives')
grid
legend('Location','best')
.
8 commentaires
Star Strider
le 27 Jan 2023
My pleasure!
If my Answer helped you solve your problem, please Accept it!
.
Steven Lord
le 16 Jan 2023
The ischange, islocalmin, and/or islocalmax functions may be of use to you, as might the corresponding Live Editor Tasks Find Change Points and Find Local Extrema.
0 commentaires
Voir également
Catégories
En savoir plus sur Time Series dans Help Center et File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!