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

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.

Answer 1

[Sam Chak]

Hi @Yew Jen Chong

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])

[Yew Jen Chong]

Thank you @Sam Chak for your help.

Answer 2

[KSSV]

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')

[Yew Jen Chong]

Thank you @KSSV for your help also