org.apache.commons.math3.analysis.interpolation

Class BicubicInterpolatingFunction

java.lang.Object

org.apache.commons.math3.analysis.interpolation.BicubicInterpolatingFunction

All Implemented Interfaces:

BivariateFunction

public class BicubicInterpolatingFunction
extends java.lang.Object
implements BivariateFunction

Function that implements the bicubic spline interpolation.

Since:

3.4

Field Summary

Fields

Modifier and Type	Field and Description
private static double[][]	AINV Matrix to compute the spline coefficients from the function values and function derivatives values
private static int	NUM_COEFF Number of coefficients.
private BicubicFunction[][]	splines Set of cubic splines patching the whole data grid
private double[]	xval Samples x-coordinates
private double[]	yval Samples y-coordinates

Constructor Summary

Constructors

Constructor and Description
BicubicInterpolatingFunction(double[] x, double[] y, double[][] f, double[][] dFdX, double[][] dFdY, double[][] d2FdXdY)

Method Summary

Methods

Modifier and Type	Method and Description
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.
boolean	isValidPoint(double x, double y) Indicates whether a point is within the interpolation range.
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

NUM_COEFF

private static final int NUM_COEFF

Number of coefficients.

See Also:

Constant Field Values

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 BicubicFunction[][] splines

Set of cubic splines patching the whole data grid

Constructor Detail

BicubicInterpolatingFunction

public BicubicInterpolatingFunction(double[] x,
                            double[] y,
                            double[][] f,
                            double[][] dFdX,
                            double[][] dFdY,
                            double[][] d2FdXdY)
                             throws DimensionMismatchException,
                                    NoDataException,
                                    NonMonotonicSequenceException

Parameters:

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

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

f - Values of the function on every grid point.

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

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

d2FdXdY - 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.

NonMonotonicSequenceException - if x or y are not strictly increasing.

NoDataException - if any of the arrays has zero length.

Method Detail

value

public double value(double x,
           double y)
             throws OutOfRangeException

Compute the value for the function.

Specified by:

value in interface BivariateFunction

Parameters:

x - Abscissa for which the function value should be computed.

y - Ordinate for which the function value should be computed.

Returns:

the value.

Throws:

OutOfRangeException

isValidPoint

public boolean isValidPoint(double x,
                   double y)

Indicates whether a point is within the interpolation range.

Parameters:

x - First coordinate.

y - Second coordinate.

Returns:

true if (x, y) is a valid point.

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.

Throws:

OutOfRangeException - if c is out of the range defined by the boundary 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)
• f_x(0,0)
• f_x(1,0)
• f_x(0,1)
• f_x(1,1)
• f_y(0,0)
• f_y(1,0)
• f_y(0,1)
• f_y(1,1)
• f_xy(0,0)
• f_xy(1,0)
• f_xy(0,1)
• f_xy(1,1)

where the subscripts indicate the partial derivative with respect to the corresponding variable(s).

Parameters:

beta - List of function values and function partial derivatives values.

Returns:

the spline coefficients.