Loop to calculate area under curve using rectangle methode

Hello everyone I have a graph plotted in Matlab (no function), as data was imported via Excel, I am looking for a loop to calculate the area under the curve of each interval and then add them to get the entire area

Here's how my graph look like

[Akira Agata]

How about using trapz function, instead of trying rectangle method. Or, do you have to try rectangle method for some reason?

https://jp.mathworks.com/help/matlab/ref/trapz.html?lang=en

[Andre]

Actually, I have a research about the rectangular method, that's why

Answer 1

[Akira Agata]

Sorry for my late response. Here is an simple example.

% Sample data
dx = pi/10;
x = 0:dx:2*pi;
y = 1+sin(x);

% integral of y = f(x) via trapezoidal method (S1) and rectangle method (S2)
S1 = trapz(x,y);
S2 = sum(y*dx);