Class PolynomialSplineFunction
 java.lang.Object

 org.apache.commons.math4.legacy.analysis.polynomials.PolynomialSplineFunction

 All Implemented Interfaces:
DoubleUnaryOperator
,UnivariateDifferentiableFunction
,UnivariateFunction
public class PolynomialSplineFunction extends Object implements UnivariateDifferentiableFunction
Represents a polynomial spline function.A polynomial spline function consists of a set of interpolating polynomials and an ascending array of domain knot points, determining the intervals over which the spline function is defined by the constituent polynomials. The polynomials are assumed to have been computed to match the values of another function at the knot points. The value consistency constraints are not currently enforced by
PolynomialSplineFunction
itself, but are assumed to hold among the polynomials and knot points passed to the constructor.N.B.: The polynomials in the
polynomials
property must be centered on the knot points to compute the spline function values. See below.The domain of the polynomial spline function is
[smallest knot, largest knot]
. Attempts to evaluate the function at values outside of this range generate IllegalArgumentExceptions.The value of the polynomial spline function for an argument
x
is computed as follows: The knot array is searched to find the segment to which
x
belongs. Ifx
is less than the smallest knot point or greater than the largest one, anIllegalArgumentException
is thrown.  Let
j
be the index of the largest knot point that is less than or equal tox
. The value returned ispolynomials[j](x  knot[j])


Constructor Summary
Constructors Constructor Description PolynomialSplineFunction(double[] knots, PolynomialFunction[] polynomials)
Construct a polynomial spline function with the given segment delimiters and interpolating polynomials.

Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description double[]
getKnots()
Get an array copy of the knot points.int
getN()
Get the number of spline segments.PolynomialFunction[]
getPolynomials()
Get a copy of the interpolating polynomials array.boolean
isValidPoint(double x)
Indicates whether a point is within the interpolation range.PolynomialSplineFunction
polynomialSplineDerivative()
Get the derivative of the polynomial spline function.double
value(double v)
Compute the value for the function.DerivativeStructure
value(DerivativeStructure t)
Simple mathematical function.
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface java.util.function.DoubleUnaryOperator
andThen, compose

Methods inherited from interface org.apache.commons.math4.legacy.analysis.UnivariateFunction
applyAsDouble




Constructor Detail

PolynomialSplineFunction
public PolynomialSplineFunction(double[] knots, PolynomialFunction[] polynomials) throws NullArgumentException, NumberIsTooSmallException, DimensionMismatchException, NonMonotonicSequenceException
Construct a polynomial spline function with the given segment delimiters and interpolating polynomials. The constructor copies both arrays and assigns the copies to the knots and polynomials properties, respectively. Parameters:
knots
 Spline segment interval delimiters.polynomials
 Polynomial functions that make up the spline. Throws:
NullArgumentException
 if either of the input arrays isnull
.NumberIsTooSmallException
 if knots has length less than 2.DimensionMismatchException
 ifpolynomials.length != knots.length  1
.NonMonotonicSequenceException
 if theknots
array is not strictly increasing.


Method Detail

value
public double value(double v)
Compute the value for the function. SeePolynomialSplineFunction
for details on the algorithm for computing the value of the function. Specified by:
value
in interfaceUnivariateFunction
 Parameters:
v
 Point for which the function value should be computed. Returns:
 the value.
 Throws:
OutOfRangeException
 ifv
is outside of the domain of the spline function (smaller than the smallest knot point or larger than the largest knot point).

polynomialSplineDerivative
public PolynomialSplineFunction polynomialSplineDerivative()
Get the derivative of the polynomial spline function. Returns:
 the derivative function.

value
public DerivativeStructure value(DerivativeStructure t)
Simple mathematical function.UnivariateDifferentiableFunction
classes compute both the value and the first derivative of the function. Specified by:
value
in interfaceUnivariateDifferentiableFunction
 Parameters:
t
 function input value Returns:
 function result
 Since:
 3.1

getN
public int getN()
Get the number of spline segments. It is also the number of polynomials and the number of knot points  1. Returns:
 the number of spline segments.

getPolynomials
public PolynomialFunction[] getPolynomials()
Get a copy of the interpolating polynomials array. It returns a fresh copy of the array. Changes made to the copy will not affect the polynomials property. Returns:
 the interpolating polynomials.

getKnots
public double[] getKnots()
Get an array copy of the knot points. It returns a fresh copy of the array. Changes made to the copy will not affect the knots property. Returns:
 the knot points.

isValidPoint
public boolean isValidPoint(double x)
Indicates whether a point is within the interpolation range. Parameters:
x
 Point. Returns:
true
ifx
is a valid point.

