How to find fwhm for each peak?

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?

[Rik]

The easiest way would be split your data, so each chunk only contains 1 peak. Have you tried that?

This time I edited your question for you. Next time, please use the tools explained on this page.

[fitri zabudin]

I never tried because I had no idea. Can you tell me what you mean by dividing one by one because this is the first time I used matlab. Sorry for bothering you and thanks for your help.

[Rik]

If you have never used Matlab before, you should consider a tutorial. I can recommend the Onramp tutorial (which is provided for free by Mathworks).

[Image Analyst]

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.

[fitri zabudin]

@Image Analystthis is my actual data for "A" and the picture is the peak that I mean

Answer 1

[Star Strider]

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.

[fitri zabudin]

Thanks for ur feedback. I will try to use this idea.

[Star Strider]

As always, my pleasure!

[Braulio Rodriguez]

me too, I'm running in a similar "problem". I actually want to get FWHM only of the most important peak. Here there seems to be an overlapping with some intensity at the darkets pixels of my image (close to 0). I tried to equate the first pixels to 0 (as to not been considered the 'highest' intensity), and then apply the common FWHM function. But, it works sometimes but no all the time. Therefore, I need an alternative approach

[Braulio Rodriguez]

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]

@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.

.