How to determine the start time and the end time of the signal

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Yew Jen Chong
Yew Jen Chong on 16 Jun 2022
Commented: Yew Jen Chong on 16 Jun 2022
Hi, I want to find the start time and the end time of the signal as shown in figure below.
I tried using "findchangepts" command to identify the both time but the x-axis is incorrect. Is someone know what is the reason?
In addition, I also not sure how accurate it is by using this method.
findchangepts(signal.CurrentRMS_amp_,'MaxNumChanges',3, 'Statistic','rms')
Is there any methods to find the time accurately?
Any advice would be appreciated.
Thank you.

Accepted Answer

Sam Chak
Sam Chak on 16 Jun 2022
Alternatively, try this. The findchangepts function actually works.
T = readtable('https://www.mathworks.com/matlabcentral/answers/uploaded_files/1033920/signal.csv');
Warning: Column headers from the file were modified to make them valid MATLAB identifiers before creating variable names for the table. The original column headers are saved in the VariableDescriptions property.
Set 'VariableNamingRule' to 'preserve' to use the original column headers as table variable names.
t = T.(1);
y = T.(2);
ipt = findchangepts(y, 'MaxNumChanges', 10);
Tstart = t(ipt(1))
Tstart = 1.1100
Tfinal = t(ipt(end))
Tfinal = 1.6130
plot(t, y)
hold on
plot(Tstart, y(ipt(1)), 'ro', 'linewidth', 1.5, 'MarkerSize', 14)
plot(Tfinal, y(ipt(end)), 'ro', 'linewidth', 1.5, 'MarkerSize', 14)
xlim([1.05 1.65])

More Answers (1)

KSSV
KSSV on 16 Jun 2022
T = readtable('https://in.mathworks.com/matlabcentral/answers/uploaded_files/1033920/signal.csv') ;
Warning: Column headers from the file were modified to make them valid MATLAB identifiers before creating variable names for the table. The original column headers are saved in the VariableDescriptions property.
Set 'VariableNamingRule' to 'preserve' to use the original column headers as table variable names.
t = T.(1) ;
x = T.(2) ;
idx = x>0.1 ;
plot(t,x,'r',t(idx),x(idx),'b')

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