MATLAB Answers

Integrate with Simpson's Rule

57 views (last 30 days)
Danny Helwegen
Danny Helwegen on 13 Jan 2019
Edited: David Goodmanson on 14 Jan 2019
Hi i have, probably an easy, problem. I made a function (see the outcome below) and i need to integrate the outcome, but since the interval is small the subscript indices aren't integers. This is the problem:
f =
0.0028 0.1333 0.2667 0.4000 0.5333 0.6667 0.8000 0.9333 1.0667 1.1972
So then i use the Simpson Rule:
%interval is [0,1.2]
a = 0; b = 1.2; n =10; h = (b-a)/n
xi=a:h:b
I = h/3*(f(xi(1))+2*sum(f(xi(3:2:end-2)))+4*sum(f(xi(2:2:end)))+f(xi(end)));
But i get the error: Subscript indices must either be real positive integers or logicals.
How can I solve this?

Accepted Answer

Matt J
Matt J on 14 Jan 2019
Edited: Matt J on 14 Jan 2019
It doesn't look like you xi should be involved, since you already have the samples of f
I = h/3*(f((1))+2*sum(f((3:2:end-2)))+4*sum(f((2:2:end)))+f((end)));
  1 Comment
David Goodmanson
David Goodmanson on 14 Jan 2019
Addressing f_i directly (assuming the x_i are equally spaced) is the right method, but the problem is that f has an even number of points. So the end point f(10) gets a weight of 5, not 1.

Sign in to comment.

More Answers (0)

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by