org.apache.commons.math.analysis.interpolation
Class BicubicSplineInterpolatingFunction

java.lang.Object
  org.apache.commons.math.analysis.interpolation.BicubicSplineInterpolatingFunction

All Implemented Interfaces:

BivariateRealFunction

public class BicubicSplineInterpolatingFunction
extends Object
implements BivariateRealFunction

Function that implements the bicubic spline interpolation.

Since:

2.1

Version:

$Revision$ $Date$

Field Summary

private static double[][]	AINV Matrix to compute the spline coefficients from the function values and function derivatives values
private BicubicSplineFunction[][]	splines Set of cubic splines pacthing the whole data grid
private double[]	xval Samples x-coordinates
private double[]	yval Samples y-coordinates

Constructor Summary

BicubicSplineInterpolatingFunction(double[] x, double[] y, double[][] z, double[][] dZdX, double[][] dZdY, double[][] dZdXdY)

Method Summary

private double[]	computeSplineCoefficients(double[] beta) Compute the spline coefficients from the list of function values and function partial derivatives values at the four corners of a grid element.
private int	searchIndex(double c, double[] val)
double	value(double x, double y) Compute the value for the function.

Methods inherited from class java.lang.Object

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

Field Detail

AINV

private static final double[][] AINV

Matrix to compute the spline coefficients from the function values and function derivatives values

xval

private final double[] xval

Samples x-coordinates

yval

private final double[] yval

Samples y-coordinates

splines

private final BicubicSplineFunction[][] splines

Set of cubic splines pacthing the whole data grid

Constructor Detail

BicubicSplineInterpolatingFunction

public BicubicSplineInterpolatingFunction(double[] x,
                                          double[] y,
                                          double[][] z,
                                          double[][] dZdX,
                                          double[][] dZdY,
                                          double[][] dZdXdY)
                                   throws DimensionMismatchException

Parameters:

x - Sample values of the x-coordinate, in increasing order

y - Sample values of the y-coordinate, in increasing order

z - Values of the function on every grid point

dZdX - Values of the partial derivative of function with respect to x on every grid point

dZdY - Values of the partial derivative of function with respect to y on every grid point

dZdXdY - Values of the cross partial derivative of function on every grid point

Throws:

DimensionMismatchException - if the various arrays do not contain the expected number of elements.

IllegalArgumentException - if x or y are not strictly increasing.

Method Detail

value

public double value(double x,
                    double y)

Compute the value for the function.

Specified by:

value in interface BivariateRealFunction

Parameters:

x - abscissa for which the function value should be computed

y - ordinate for which the function value should be computed

Returns:

the value

searchIndex

private int searchIndex(double c,
                        double[] val)

Parameters:

c - coordinate

val - coordinate samples

Returns:

the index in val corresponding to the interval containing c, or -1 if c is out of the range defined by the end values of val

computeSplineCoefficients

private double[] computeSplineCoefficients(double[] beta)

Compute the spline coefficients from the list of function values and function partial derivatives values at the four corners of a grid element. They must be specified in the following order:

• f(0,0)
• f(1,0)
• f(0,1)
• f(1,1)
• fx(0,0)
• fx(1,0)
• fx(0,1)
• fx(1,1)
• fy(0,0)
• fy(1,0)
• fy(0,1)
• fy(1,1)
• fxy(0,0)
• fxy(1,0)
• fxy(0,1)
• fxy(1,1)

Parameters:

beta - List of function values and function partial derivatives values

Returns:

the spline coefficients