use trapz to calculate the peak area

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Paul
Paul 2015-1-9
Hello,
Im trying to use the trapz function to calculate the peak area of selected peaks. But it doesn't work and I don't know what is the failure.
My x-axis (mz) is function and my mass spectrometry data (sample) is in a csv-file, it consists of 200 spectras with 17000 data points.
The plot looks fine and all spectras are mapped, but I dont't know how to use the trapz function.
1) Is trapz the correct function for my problem? 2) How can I integrate only in a small area around the peak (from a to b)? 3) How can I calculate the area between a baseline and a peak?
Im a bit frustrated because I can't find a solution in the forum or on mathworks.com! :-(
mz: 17000x1 double
sample: 17000x200 double
if true
% code
sample = importdata('Daten.csv');
x = [0.0005:0.0005:8.5];
t = x.';
clear x;
mz = (2.5347*(t-0.169).^2);
clear t;
figure(1) plot(mz, sample(:,:)) grid
xlabel('Masse/Ladung (m/z)'); ylabel('Intensität'); title('Massenspektren');
a = 27.5; b = 28,5; c = 0.095
area_1 = trapz(mz, sample(:,1)); ???
end
Thx for your help!
Kind regards Paul

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