How do I do numerical integration of a vector in MATLAB?

matlab numerical-integration
user330860 picture user330860 · May 18, 2010 · Viewed 60.5k times · Source

I have a vector of 358 numbers. I'd like to make a numerical integration of this vector, but I don't know the function of this one.

I found that we can use trapz or quad, but i don't really understand how to integrate without the function.

Answer

Doresoom picture Doresoom · May 19, 2010

If you know the horizontal spacing of your vector, you can use trapz in order to integrate it without the function. For example, to integrate y=sin(x) from 0 to pi with 358 sections, 

x=0:pi/357:pi;
y=sin(x);
area=trapz(x,y);

If you just use trapz(y), you'll get a much larger number, since the default distance between points is assumed to be 1. This problem can be fixed by multiplying by the distance between x points:

area=pi/357*trapz(y);

Related questions

How to overcome singularities in numerical integration (in Matlab or Mathematica)

I want to numerically integrate the following: where and a, b and β are constants which for simplicity, can all be set to 1. Neither Matlab using dblquad, nor Mathematica using NIntegrate can deal with the singularity created by the denominator. Since …

Read More
Read .mat files in Python

Is it possible to read binary MATLAB .mat files in Python? I've seen that SciPy has alleged support for reading .mat files, but I'm unsuccessful with it. I installed SciPy version 0.7.0, and I can't find the loadmat() method.

Read More
How do I iterate through each element in an n-dimensional matrix in MATLAB?

I have a problem. I need to iterate through every element in an n-dimensional matrix in MATLAB. The problem is, I don't know how to do this for an arbitrary number of dimensions. I know I can say for i = 1:…

Read More