How to calculate the width that contains 60% of the total area of peaks?

Question

Lope 2022-4-25

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https://ww2.mathworks.cn/matlabcentral/answers/1704290-how-to-calculate-the-width-that-contains-60-of-the-total-area-of-peaks

评论： Lope 2022-4-25

So starting from the center (where the max peak always lies), I want to calculate automatically the width that contains 60% of the total area under multiple peaks. How can I do that? Attached is the normalized intensities and positions.

Below is the code to an attempt to get the contribution of the main peak only from the total area:

TotalArea=trapz(x2,Int);

lims = (x2>= -3.90625E-5 ) & (x2<= 3.90625E-5); %manually selected

MainPeakArea=trapz(x2(lims),Int(lims));

MainLobePower = (MainPeakArea/TotalArea)*100;

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Answer 1

Chunru 2022-4-25

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https://ww2.mathworks.cn/matlabcentral/answers/1704290-how-to-calculate-the-width-that-contains-60-of-the-total-area-of-peaks#answer_950235

在 MATLAB Online 中打开

load position

load Intensity

whos

Name Size Bytes Class Attributes Int 1x2048 16384 double ans 1x38 76 char cmdout 1x33 66 char x2 1x2048 16384 double

plot(x2, Int); hold on

% find the max

[maxI, idx] = max(Int);

maxX = x2(idx)

maxX = 0

n = length(x2);

Atotal = trapz(x2, Int);

for w=1:length(x2)

ii = max(idx-w, 1):min(idx+w, n);

A = trapz(x2(ii), Int(ii));

if A/Atotal>=0.6

break

end

area(x2(ii), Int(ii));

plot(x2(idx), Int(idx), 'r^');

xlim([-1 1]*1e-3)

title(sprintf('Width: %g - %g', x2(ii(1)), x2(ii(end)) ));

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Lope 2022-4-25

@Chunru, Thank you so much for the help.

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Answer 2

Bruno Luong 2022-4-25

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https://ww2.mathworks.cn/matlabcentral/answers/1704290-how-to-calculate-the-width-that-contains-60-of-the-total-area-of-peaks#answer_950240

编辑：Bruno Luong 2022-4-25

在 MATLAB Online 中打开

load Intensity.mat
load position.mat
ifun=@(x) interp1(x2,Int,x,'linear','extrap');
I0=integral(ifun,x2(1),x2(end))
I0 = 5.6250e-05
x = fzero(@(x) integral(ifun,-x,x)-0.6*I0,0) % the interval is (-x,x) width is 2*x
x = 3.1468e-05