# how to find duration of peak; starting and ending points

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Raheema Al Karim Damani on 25 Feb 2020
Answered: Lam Ha on 9 Jun 2023
I've used findpeaks to isolate the largest peak in my signal. I wanted some help in finding the duration of the peak aka the starting and ending points of this peak, so that I could calculate area under curve? Right now Im having to visually inspect and pick arbitrary points to define this start and end points.

Star Strider on 25 Feb 2020
Experiment with ths ischange function, and if you have the Signal Processing Toolbox, the findchangepts function.
Raheema Al Karim Damani on 25 Feb 2020
Star Strider on 26 Feb 2020
As always, my pleasure!

Sindar on 25 Feb 2020
widths are an optional output from findpeaks:
[pks,locs,widths,~] = findpeaks(data);
Sindar on 25 Feb 2020
Alternatively, you could potentially define the starting and ending points using findpeaks on the negative of your data.
Raheema Al Karim Damani on 25 Feb 2020
Edited: Raheema Al Karim Damani on 25 Feb 2020
I believe that it finds the widths from the half prominence or half height, which would not accurately characterize the starting and ending points.
Also, I would like to find the index (x values) of the peak based on start and end points

Alexis on 9 Jul 2021
Edited: Alexis on 9 Jul 2021
I had a similar issue, although I was working with biological signals. You could try the function I wrote to solve my problem: https://uk.mathworks.com/matlabcentral/fileexchange/81066-breathtimes?s_tid=srchtitle

Lam Ha on 9 Jun 2023
Hi, I'm doing my research and meet the same problems as you. Have you calculated the peak duration? Can you share to me how to calculate the peak duration? Thank you so much in advance