How can I calculate the shaded area ?

I have a representative subset of sample points as attached, and intend to calculate the shaded area from x = -40 to x = 30.

Answer 1

[Kanishk]

Dear wd,

I understand you are interested in calculating the area between a plotted line and the x-axis over the interval from (x = -40) to (x = 30).

You can achieve this using MATLAB's “trapz” function, which performs numerical integration. Below is the simple code to plot the data and compute the desired area.

% Load data from Excel 
data = readmatrix('example.xlsx');

%filter data 
xRange = [-40, 30]; 
indices = (data(:,1) >= xRange(1)) & (data(:,1) <= xRange(2));
x = data(indices, 1); 
y = data(indices, 2); 

% Plot the data 
figure; 
plot(x, y, 'k'); 
hold on; 
fill([x; flipud(x)], [y; zeros(size(y))], [0.5, 0.5, 0.5], 'FaceAlpha', 0.3, 'EdgeColor', 'none'); 
hold off; 
xlabel('X-axis'); 
ylabel('Y-axis'); 
title('Plot of X vs Y'); 

% Calculate the area under the curve 
areaUnderCurve = trapz(x, abs(y)); 
disp(['The area under the curve is: ', num2str(areaUnderCurve)]); 

To learn more please go through this official MATLAB documentation of “trapz”.

https://www.mathworks.com/help/releases/R2024a/matlab/ref/trapz.html

Hope this helps!

Thanks

[wd w]

Kanishk, thank you very much!