org.apache.commons.math4.analysis.polynomials

## Class PolynomialFunction

• java.lang.Object
• org.apache.commons.math4.analysis.polynomials.PolynomialFunction
• ### Constructor Detail

• #### PolynomialFunction

public PolynomialFunction(double[] c)
throws NullArgumentException,
NoDataException
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.
Throws:
NullArgumentException - if c is null.
NoDataException - 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 UnivariateFunction
Parameters:
x - Argument for which the function value should be computed.
Returns:
the value of the polynomial at the given point.
See Also:
UnivariateFunction.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)
throws NullArgumentException,
NoDataException
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.
Throws:
NoDataException - if coefficients is empty.
NullArgumentException - if coefficients is null.
• #### add

public PolynomialFunction add(PolynomialFunction p)
Add a polynomial to the instance.
Parameters:
p - Polynomial to add.
Returns:
a new polynomial which is the sum of the instance and p.
• #### subtract

public PolynomialFunction subtract(PolynomialFunction p)
Subtract a polynomial from the instance.
Parameters:
p - Polynomial to subtract.
Returns:
a new polynomial which is the instance minus p.
• #### negate

public PolynomialFunction negate()
Negate the instance.
Returns:
a new polynomial with all coefficients negated
• #### multiply

public PolynomialFunction multiply(PolynomialFunction p)
Multiply the instance by a polynomial.
Parameters:
p - Polynomial to multiply by.
Returns:
a new polynomial equal to this times p
• #### differentiate

protected static double[] differentiate(double[] coefficients)
throws NullArgumentException,
NoDataException
Returns the coefficients of the derivative of the polynomial with the given coefficients.
Parameters:
coefficients - Coefficients of the polynomial to differentiate.
Returns:
the coefficients of the derivative or null if coefficients has length 1.
Throws:
NoDataException - if coefficients is empty.
NullArgumentException - if coefficients is null.
• #### 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.

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