How to find fwhm for each peak?
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fitri zabudin
on 10 Feb 2021
Commented: Star Strider
on 19 Sep 2021
this is my coding in matlab. A is the result from picoscope. the result get from detecting lightning signal.
y = A(:,1);
x = (-0.6:4.000000046744390e-07:1.4);
plot(x,y)
title("FA-31")
ylabel("voltage(V)")
xlabel("time(s)")
vmax = max(y);
vmin = min (y);
%Find the half max value.
halfMax = max(y) / 2;
% Find where the data first drops below half the max.
index1 = find(y >= halfMax, 1, 'first');
% Find where the data last rises above half the max.
index2 = find(y >= halfMax, 1, 'last');
fwhm = index2-index1 + 1; % FWHM in indexes
% if you have an x vector
fwhmx = x(index2) - x(index1);
The formula I use in matlab for find fwhm is I get from Internet. Can u help me how to get the fwhm for all peak?
5 Comments
Image Analyst
on 10 Feb 2021
What's your definition of "peak"? How many do you say are there? Do you want to attach "A" so we can try things with your actual data?
save('answers.mat', 'A');
Then attach 'answers.mat' with the paper clip icon.
Accepted Answer
Star Strider
on 10 Feb 2021
The Signal Processing Toolbox findpeaks function can return the FWHM of every peak. See the documentation sections on Determine Peak Widths and w for the necessary details. To return only the results from the largest or most prominent peaks, other name-value pair arguments will allow selections based on these (and other) criteria.
5 Comments
Braulio Rodriguez
on 19 Sep 2021
Edited: Braulio Rodriguez
on 19 Sep 2021
I'm interested on the broad peak. The peaks between roughly 0-5 pixels mess up my FWHM calculation. I cannot exclude these peaks on the basis of sole intensity, as the intensity varies from picture to picture, but the location of the first 'artificial' peaks are always approx. on the same range.
Star Strider
on 19 Sep 2021
@Braulio Rodriguez — See I am trying to find the full width at half max value and plot the waveform with markers for an appropriate example.
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