org.apache.commons.math3.analysis.integration.gauss

## Class GaussIntegrator

- java.lang.Object
- - org.apache.commons.math3.analysis.integration.gauss.GaussIntegrator

    public class GaussIntegrator
    extends java.lang.Object

Class that implements the Gaussian rule for `integrating` a weighted function.

Since:
  3.1
Version:
  $Id: GaussIntegrator.java 1382197 2012-09-07 22:35:01Z erans $

### Field Summary

Fields
`private double[]` `points` Nodes.
`private double[]` `weights` Nodes weights.

### Constructor Summary

Constructors
Constructor and Description
`GaussIntegrator(double[] points, double[] weights)` Creates an integrator from the given `points` and `weights`.
`GaussIntegrator(Pair<double[],double[]> pointsAndWeights)` Creates an integrator from the given pair of points (first element of the pair) and weights (second element of the pair.

### Method Summary

Methods
`int` `getNumberOfPoints()`
`double` `integrate(UnivariateFunction f)` Returns an estimate of the integral of `f(x) * w(x)`, where `w` is a weight function that depends on the actual flavor of the Gauss integration scheme.

### Methods inherited from class java.lang.Object

`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

### Field Detail

#### points

    private final double[] points

Nodes.

#### weights

    private final double[] weights

Nodes weights.

### Constructor Detail

#### GaussIntegrator

    public GaussIntegrator(double[] points,
                   double[] weights)
                    throws NonMonotonicSequenceException

Creates an integrator from the given `points` and `weights`. The integration interval is defined by the first and last value of `points` which must be sorted in increasing order.

Parameters:
  `points` - Integration points.
  `weights` - Weights of the corresponding integration nodes.
Throws:
  `NonMonotonicSequenceException` - if the `points` are not sorted in increasing order.

#### GaussIntegrator

    public GaussIntegrator(Pair<double[],double[]> pointsAndWeights)
                    throws NonMonotonicSequenceException

Creates an integrator from the given pair of points (first element of the pair) and weights (second element of the pair.

Parameters:
  `pointsAndWeights` - Integration points and corresponding weights.
Throws:
  `NonMonotonicSequenceException` - if the `points` are not sorted in increasing order.
See Also:
  `GaussIntegrator(double[], double[])`

### Method Detail

#### integrate

    public double integrate(UnivariateFunction f)

Returns an estimate of the integral of `f(x) * w(x)`, where `w` is a weight function that depends on the actual flavor of the Gauss integration scheme. The algorithm uses the points and associated weights, as passed to the `constructor`.

Parameters:
  `f` - Function to integrate.
Returns:
  the integral of the weighted function.

#### getNumberOfPoints

    public int getNumberOfPoints()

Returns:
  the order of the integration rule (the number of integration points).