# What is the meaning of "width" and "prominences" in findpeaks

67 views (last 30 days)
Matlaber on 7 Feb 2019
Commented: Star Strider on 12 Jul 2021
It said that:
[pks,locs,w,p] = findpeaks(data) additionally returns the widths of the peaks as the vector w and the prominences of the peaks as the vector p.
w is the widths of the peaks as the vector w
I still unable to find out how they calculate the width.
In the example below:
x = linspace(0,1,1000);
Pos = [1 2 3 5 7 8]/10;
Hgt = [4 4 2 2 2 3];
Wdt = [3 8 4 3 4 6]/100;
for n = 1:length(Pos)
Gauss(n,:) = Hgt(n)*exp(-((x - Pos(n))/Wdt(n)).^2);
end
PeakSig = sum(Gauss);
Plot the individual curves and their sum
plot(x,Gauss,'--',x,PeakSig)
grid
findpeaks(PeakSig,x,'MinPeakProminence',2,'Annotate','extents','WidthReference','halfheight')
[pks,locs,w,p]= findpeaks(PeakSig,x,'MinPeakProminence', 2,'Annotate','extents','WidthReference','halfheight')
title('Signal Peak Widths')
w =
0.2352 0.1725
p =
4.8721 3.0028
Is the w is the width (half-height) and p is height as pointed in the plot?

Star Strider on 7 Feb 2019
Is the w is the width (half-height) and p is height as pointed in the plot?
Your interpretation of ‘p’ is correct. The value of ‘w’ returned depends on how you define 'WidthReference' (link). You can define it to be full width half maximum (FWHM) if you define it as 'halfheight'.
Star Strider on 12 Jul 2021
It would be necessary to know the half-prominence height (‘y’ value that is apparently half the ‘y’ value of the tallest peak) and then use interp1 to calculate at least one of the ‘x’ values, then adding or subtracting the FWHM value to get the second ‘x’ value. (That could be something of a challenge in the examples in this illustration.)