I want to find the area of the graph

I'd like to get the area of the part drawn in red using threshold.

I thought I'd use a specific value or slope to get a range and then get an area.

And may I know how to remove the noise from the signal?

% plot(xy(1,:),xy(2,:));

Answer 1

[Star Strider]

Try this —

LD = load('x,y.mat');
x = LD.xy(1,:);
y = LD.xy(2,:);

yf = sgolayfilt(y, 3, 1001);                                        % Filter Signal
k = islocalmin(yf, 'MinProminence',0.0001);                         % Find Local Minima
idx = find(k);                                                      % Numeric Index

idxrng = idx(1):idx(2);                                             % Index Range
xp = x(idxrng);                                                     % X-Vector
yp = y(idxrng);                                                     % Y-Vector
posarea = trapz(xp(yp>0),yp(yp>0));                                 % Area Above y=0
negarea = trapz(xp(yp<=0),yp(yp<=0));                               % Area below y=0
totarea = posarea - negarea                                         % Total Area
uncorrarea = trapz(xp,yp);                                          % Uncorrectred Area (For Comparison)

figure
plot(x, y)
hold on
plot(x(k), yf(k), '+r', 'MarkerSize',10)
plot(x, yf, 'LineWidth',1.25)
hold off
grid
legend('Original Data','Local Minima','Filtered Data', 'Location','best')
text(0.5, 0.0125, sprintf('Area = %.4f',totarea)

The trapz function integrates with respect to zero, so anything below zero is subtracted from the area above zero. This code calculates the peak area without (‘uncorrarea’) and with (‘totarea’) the baseline correction.

The area of the peak with the uncorrected baseline is and the peak area with the corrected baseline is .

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[대수 김]

Thank you very much.

I will apply various things based on the code and function you wrote me.

I hope you have a good day.

[Star Strider]

My pleasure!

If my Answer helped you solve your problem, please Accept it!

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