use trapz to calculate the peak area

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