Trapezoidal rule with unevenly spaced data points

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Georgia Platt
Georgia Platt el 22 de Sept. de 2022
Comentada: Walter Roberson el 22 de Sept. de 2022
I am having a lot of trouble using the trapezoidal method on matlab to determine the area under the curve with no function, just unevenly spaced data points:
(0,0), (1,5), (5,8), (9,6), (3,10), (0,11)
I have absolutely no idea where to start.
  6 comentarios
James Tursa
James Tursa el 22 de Sept. de 2022
Editada: James Tursa el 22 de Sept. de 2022
@Georgia Platt If you know how to do it by hand, why can't you code that method into MATLAB? Especially once you look at the formulas in the links above. For two points (x1,y1) and (x2,y2) with the ordering x1<x2, the area formed by the trapezoid is simply (x2-x1)*(y1+y2)/2, so why can't you write a loop to sum these up?
Walter Roberson
Walter Roberson el 22 de Sept. de 2022
You can decompose into shapes. There is an initial triangle, and you can get the area for that as 1/2 base times height. There are then a series of trapazoids, and you can calculate their areas. Then there is a final triangle and 1/2 base times height for it. Add the areas all together.
... which is what trapz() will do for you.

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Matt J
Matt J el 22 de Sept. de 2022
See trapz.

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