Trapezoidal Integrator

The net.sf.doodleproject.numerics4j.integration.TrapezoidalIntegrator class provides an implementation of the extended trapezoidal rule.

Evaluating definite integrals using the trapezoidal rule involves creating a TrapezoidalIntegrator object for a particular net.sf.doodleproject.numerics4j.function.Function object. Once, the integrator is created, definite integrals can be evaluated by calling the integrate method providing the limits of integration. Here is an example of evaluating integrals for sine: 

Function sine = new Function() {
    public double evaluate(double x) {
        return Math.sin(x);
    }
};

TrapezoidalIntegrator integrator = new TrapezoidalIntegrator(sine);

// integrate sine from 0 to Pi.
double two = integrator.integrate(0.0, Math.PI);

// integrate sine from Pi/2 to 2 Pi.
double one = integrator.integrate(Math.PI / 2.0, Math.PI);