Class PolynomialFunction

java.lang.Object
uk.ac.starlink.dpac.math.PolynomialFunction

public class PolynomialFunction extends Object
Immutable representation of a real polynomial function with real coefficients.

Horner's Method is used to evaluate the function.

  • Constructor Summary

    Constructors
    Constructor
    Description
    PolynomialFunction(double[] c)
    Construct a polynomial with the given coefficients.
  • Method Summary

    Modifier and Type
    Method
    Description
    int
    Returns the degree of the polynomial.
    boolean
    protected static double
    evaluate(double[] coefficients, double argument)
    Uses Horner's Method to evaluate the polynomial with the given coefficients at the argument.
    double[]
    Returns a copy of the coefficients array.
    int
    Returns a string representation of the polynomial.
    double
    value(double x)
    Compute the value of the function for the given argument.

    Methods inherited from class java.lang.Object

    clone, finalize, getClass, notify, notifyAll, wait, wait, wait
  • Constructor Details

    • 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 index of the last non-null element of the array, or 0 if all elements are null.

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

      Parameters:
      c - Polynomial coefficients.
  • Method Details

    • 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]

      Parameters:
      x - Argument for which the function value should be computed.
      Returns:
      the value of the polynomial at the given point.
    • 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 - Coefficients of the polynomial to evaluate.
      argument - Input value.
      Returns:
      the value of the polynomial.
    • toString

      public String toString()
      Returns a string representation of the polynomial.

      The representation is user oriented. Terms are displayed lowest degrees first. The multiplications signs, coefficients equals to one and null terms are not displayed (except if the polynomial is 0, in which case the 0 constant term is displayed). Addition of terms with negative coefficients are replaced by subtraction of terms with positive coefficients except for the first displayed term (i.e. we display -3 for a constant negative polynomial, but 1 - 3 x + x^2 if the negative coefficient is not the first one displayed).

      Overrides:
      toString in class Object
      Returns:
      a string representation of the polynomial.
    • hashCode

      public int hashCode()
      Overrides:
      hashCode in class Object
    • equals

      public boolean equals(Object obj)
      Overrides:
      equals in class Object