MATLAB: How to calculate area under each peak from the plot

peak ara

I want to calculate the aria under my plot and after for each peack. How can i do that? I have attached the data for plot and a picture of each zone that i need the area.

Best Answer

See if this does what you want:

D = load('data for plot.txt');
x = 0:numel(D)-1;                                               % Choose The Appropriate Vector For The Most Accurate Results
[pks,locs] = findpeaks(-D);                                     % ‘Trough’ Minima Between Peaks
IntTot = cumtrapz(x,D);                                         % Integrate
IntPks = diff(IntTot(locs));                                    % Peak Areas
IntPks =
        0.45474
        0.08047
        0.15185
        0.20436
        0.25881
      0.0068099

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MATLAB: Correlation between two row matrices

Like that, each value of "a" is correlated to each value of "b", but applying the formula of the correlation, the correlation of two single numbers is NaN. To compute the correlation correctly, traspose the input vectors

result  = corr(a', b');

MATLAB: How to find the peaks in the signal with descending order only

This works, with the example you provided:

pks = [100,80,60,70,50,80]';
locs = [1,2,3,4,5,6]';
dpks = diff([pks(1); pks]);                     % Non-Descending Will Be Positive

Lv = dpks <= 0;                                 % Logical Vector Mask

pks1 = pks(Lv);                                 % New Peaks

locs1 = locs(Lv);                               % New Locs

figure
plot(locs, pks, '^')
hold on
plot(locs1, pks1, 's')
hold off

It does not do any rigorous checking, and just looks ad adjacent peaks.

You can easily wrap it in a function:

function [pks1,locs1] = descending_peaks(pks,locs)
dpks = diff([pks(1); pks]);                     % Non-Descending Will Be Positive
Lv = dpks <= 0;                                 % Logical Vector Mask
pks1 = pks(Lv);                                 % New Peaks
locs1 = locs(Lv);                               % New Locs
end

Experiment to get the result you want.

Best Answer

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MATLAB: Correlation between two row matrices

MATLAB: How to find the peaks in the signal with descending order only

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