Try this:
D = load('data for peak area.txt');
idx = D >= 0.28;
chg = [find(diff(idx ~= 0)); numel(D)];
chg(1) = 1;
for k1 = 1:numel(chg)-1
segment_area(k1) = trapz(chg(k1:k1+1), D(chg(k1:k1+1)));
Q1(:,k1) = chg([k1 k1+1]);
Q2(:,k1) = D(chg([k1 k1+1]));
end
figure(1)
plot(D)
hold on
plot(Q1, Q2, 'pg')
hold off
grid
area_text = regexp(sprintf('%.2f\n', segment_area), '\n', 'split');
text(mean(Q1), ones(size(segment_area))*0.12, area_text(1:end-1), 'HorizontalAlignment','center')
Best Answer