org.apache.commons.math3.analysis.polynomials
public class PolynomialSplineFunction extends Object implements UnivariateDifferentiableFunction, DifferentiableUnivariateFunction
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:
x
belongs. If x
is less than the smallest knot point or greater
than the largest one, an IllegalArgumentException
is thrown.j
be the index of the largest knot point that is less
than or equal to x
. The value returned is polynomials[j](x  knot[j])
Constructor and Description 

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

Modifier and Type  Method and Description 

UnivariateFunction 
derivative()
Get the derivative of the polynomial spline function.

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.

DerivativeStructure 
value(DerivativeStructure t)
Simple mathematical function.

double 
value(double v)
Compute the value for the function.

public PolynomialSplineFunction(double[] knots, PolynomialFunction[] polynomials) throws NullArgumentException, NumberIsTooSmallException, DimensionMismatchException, NonMonotonicSequenceException
knots
 Spline segment interval delimiters.polynomials
 Polynomial functions that make up the spline.NullArgumentException
 if either of the input arrays is null
.NumberIsTooSmallException
 if knots has length less than 2.DimensionMismatchException
 if polynomials.length != knots.length  1
.NonMonotonicSequenceException
 if the knots
array is not strictly increasing.public double value(double v)
PolynomialSplineFunction
for details on the algorithm for
computing the value of the function.value
in interface UnivariateFunction
v
 Point for which the function value should be computed.OutOfRangeException
 if v
is outside of the domain of the
spline function (smaller than the smallest knot point or larger than the
largest knot point).public UnivariateFunction derivative()
derivative
in interface DifferentiableUnivariateFunction
public PolynomialSplineFunction polynomialSplineDerivative()
public DerivativeStructure value(DerivativeStructure t)
UnivariateDifferentiableFunction
classes compute both the
value and the first derivative of the function.
value
in interface UnivariateDifferentiableFunction
t
 function input valuepublic int getN()
public PolynomialFunction[] getPolynomials()
public double[] getKnots()
public boolean isValidPoint(double x)
x
 Point.true
if x
is a valid point.Copyright © 2003–2015 The Apache Software Foundation. All rights reserved.