I am not certain what you want.
Try this —
x = linspace(0, 20, 250);
ctrv = rand(3,1)*18;
y = sum(exp(-(x-ctrv).^2./rand(3,1))); % Generate Gaussian Peaks With Random Widths & Locations
[pks,locs,wdth] = findpeaks(y, 'WidthReference','halfheight'); % Calculate Peak Locations & FWHM Values
figure
plot(x, y)
grid
text(x(locs), pks/2, compose('%.1f',wdth), 'Horiz','center', 'Vert','bottom') % Write The FWHM Values At The Appropriate Locations On The Plot
This writes the full-width-half-maximum values at the coordinates of those values. See the documentation on the text function for details. Make appropriate changes to work with your data.
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