org.apache.commons.math.analysis
Class PolynomialFunction

java.lang.Object
  org.apache.commons.math.analysis.PolynomialFunction

All Implemented Interfaces:

DifferentiableUnivariateRealFunction, Serializable, UnivariateRealFunction

public class PolynomialFunction

extends Object

implements DifferentiableUnivariateRealFunction, Serializable

Immutable representation of a real polynomial function with real coefficients.

Horner's Method is used to evaluate the function.

Version:

$Revision: 1.12 $ $Date: 2004/07/20 12:55:01 $

See Also:

Serialized Form

Field Summary

(package private) static long

serialVersionUID Serializable version identifier

Constructor Summary

PolynomialFunction(double[] c)
Construct a polynomial with the given coefficients.

Method Summary

int	degree() Returns the degree of the polynomial
UnivariateRealFunction	derivative() Returns the derivative as a UnivariateRealFunction
protected static double[]	differentiate(double[] coefficients) Returns the coefficients of the derivative of the polynomial with the given coefficients.
protected static double	evaluate(double[] coefficients, double argument) Uses Horner's Method to evaluate the polynomial with the given coefficients at the argument.
double[]	getCoefficients() Returns a copy of the coefficients array.
PolynomialFunction	polynomialDerivative() Returns the derivative as a PolynomialRealFunction
double	value(double x) Compute the value of the function for the given argument.

Methods inherited from class java.lang.Object

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

Field Detail

serialVersionUID

static final long serialVersionUID

Serializable version identifier

See Also:

Constant Field Values

Constructor Detail

PolynomialFunction

public PolynomialFunction(double[] c)

Construct a polynomial with the given coefficients. The first element of the coefficients array is the constant term. Higher degree coefficients follow in sequence. The degree of the resulting polynomial is the length of the array minus 1.

The constructor makes a copy of the input array and assigns the copy to the coefficients property.

Parameters:

c - polynominal coefficients

Throws:

NullPointerException - if c is null

IllegalArgumentException - if c is empty

Method Detail

value

public double value(double x)

Compute the value of the function for the given argument.

The value returned is
coefficients[n] * x^n + ... + coefficients[1] * x + coefficients[0]

Specified by:

value in interface UnivariateRealFunction

Parameters:

x - the argument for which the function value should be computed

Returns:

the value of the polynomial at the given point

See Also:

UnivariateRealFunction.value(double)

degree

public int degree()

Returns the degree of the polynomial

Returns:

the degree of the polynomial

getCoefficients

public double[] getCoefficients()

Returns a copy of the coefficients array.

Changes made to the returned copy will not affect the coefficients of the polynomial.

Returns:

a fresh copy of the coefficients array

evaluate

protected static double evaluate(double[] coefficients,
                                 double argument)

Uses Horner's Method to evaluate the polynomial with the given coefficients at the argument.

Parameters:

coefficients - the coefficients of the polynomial to evaluate

argument - the input value

Returns:

the value of the polynomial

Throws:

IllegalArgumentException - if coefficients is empty

NullPointerException - if coefficients is null

differentiate

protected static double[] differentiate(double[] coefficients)

Returns the coefficients of the derivative of the polynomial with the given coefficients.

Parameters:

coefficients - the coefficients of the polynomial to differentiate

Returns:

the coefficients of the derivative or null if coefficients has length 1.

Throws:

IllegalArgumentException - if coefficients is empty

NullPointerException - if coefficients is null

polynomialDerivative

public PolynomialFunction polynomialDerivative()

Returns the derivative as a PolynomialRealFunction

Returns:

the derivative polynomial

derivative

public UnivariateRealFunction derivative()

Returns the derivative as a UnivariateRealFunction

Specified by:

derivative in interface DifferentiableUnivariateRealFunction

Returns:

the derivative function