EDU.gatech.cc.is.learning
Class Bilinear2D

java.lang.Object
  |
  +--EDU.gatech.cc.is.learning.FunctionApproximator
        |
        +--EDU.gatech.cc.is.learning.Bilinear2D

public class Bilinear2D

extends FunctionApproximator

implements java.lang.Cloneable, java.io.Serializable

Transform points from a two-dimensional space to another two dimensional space.

Introduction
The Bilinear2D is a vectorial function that transforms points from a two-dimensional space to another two-dimensional space. The transformation is specified using a grid at the domain space and associating the points at the target space that correspond to each node of the grid.

Computation
The evaluation of query points is performed using a bilinear interpolation of the target points associated with the four neighboring points to the query point.

The domain space is specified by a rectangle and a grid of points. The rectangle is defined using four numbers: min_x_limit, max_x_limit, min_y_limit, and max_y_limit. The grid of points is defined using the number of points along the x and y axes: npoints_x and npoints_y, and a bidimensional array of 2D doubles (i.e., the points in the range space).

File format
A text file can be used to define a Bilinear2D function. The format is as follows:

 min_x_limit:   [value]
 max_x_limit:   [value]
 min_y_limit:   [value]
 max_y_limit:   [value]
 npoints_x:     [r]
 npoints_y:     [s]
 [x_00],[y_00]  [x_01],[y_01] ... [x_0r],[y_0r]
 [x_10],[y_10]  [x_11],[y_11] ... [x_1r],[y_1r]
       .              .                 .
       .              .                 .
       .              .                 .
 [x_s0],[y_s0]  [x_s1],[y_s1] ... [x_sr],[y_sr]
 

Example:

 min_x_limit:   0
 max_x_limit:   50
 min_y_limit:   0
 max_y_limit:   50
 npoints_x:     5
 npoints_y:     5
 10,20  7.5,20    5,20  2.5,20   0,20
 10,15  7.5,15    5,15  2.5,15   0,15
 10,10  7.5,10    5,10  2.5,10   0,10
 10, 5  7.5, 5    5, 5  2.5, 5   0, 5
 10, 0  7.5, 0    5, 0  2.5, 0   0, 0
 

Copyright (c)1997 Georgia Tech Research Corporation

See Also:

FunctionApproximator, Serialized Form

Field Summary

double	max_x_limit Maximum value for the x variable in the domain space.
double	max_y_limit Maximum value for the y variable in the domain space.
double	min_x_limit Minimum value for the x variable in the domain space.
double	min_y_limit Minimum value for the y variable in the domain space.
int	npoints_x Number of grid points in the x axis.
int	npoints_y Number of grid points in the y axis.
double	range_x Range of the x variable in the domain space: (max_limit - min_limit).
double	range_y Range of the y variable in the domain space: (max_limit - min_limit).
double	resolution_x Resolution of the x axis: (max_limit - min_limit) / (npoints - 1)
double	resolution_y Resolution of the y axis: (max_limit - min_limit) / (npoints - 1)
protected double[][][]	table Grid of points.

Fields inherited from class EDU.gatech.cc.is.learning.FunctionApproximator

domain_dim, range_dim

Constructor Summary

Bilinear2D(double min_x_limit, double max_x_limit, int npoints_x, double min_y_limit, double max_y_limit, int npoints_y, double[][][] table)
Create an instance of a Bilinear function approximator that maps points from a two-dimensional space (x,y) to another two-dimensional space (u,v).

Bilinear2D(java.lang.String filename)
Loads the definition of a Bilinear2D function approximator from a file.

Method Summary

double[]	query(double[] point) Computes and returns the bilinear interpolation associated with the point.
double[]	query(int x, int y) Computes and returns the bilinear interpolation associated with the point.
void	saveDefinition(java.lang.String filename) Save a definition of this instance in a file.
void	update(double[] q, double[] p) Not implemented.

Methods inherited from class java.lang.Object

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

Field Detail

max_x_limit

public final double max_x_limit

Maximum value for the x variable in the domain space.

min_x_limit

public final double min_x_limit

Minimum value for the x variable in the domain space.

range_x

public final double range_x

Range of the x variable in the domain space: (max_limit - min_limit).

npoints_x

public final int npoints_x

Number of grid points in the x axis.

resolution_x

public final double resolution_x

Resolution of the x axis: (max_limit - min_limit) / (npoints - 1)

max_y_limit

public final double max_y_limit

Maximum value for the y variable in the domain space.

min_y_limit

public final double min_y_limit

Minimum value for the y variable in the domain space.

range_y

public final double range_y

Range of the y variable in the domain space: (max_limit - min_limit).

npoints_y

public final int npoints_y

Number of grid points in the y axis.

resolution_y

public final double resolution_y

Resolution of the y axis: (max_limit - min_limit) / (npoints - 1)

table

protected double[][][] table

Grid of points.

Constructor Detail

Bilinear2D

public Bilinear2D(double min_x_limit,
                  double max_x_limit,
                  int npoints_x,
                  double min_y_limit,
                  double max_y_limit,
                  int npoints_y,
                  double[][][] table)

Create an instance of a Bilinear function approximator that maps points from a two-dimensional space (x,y) to another two-dimensional space (u,v).

Bilinear2D

public Bilinear2D(java.lang.String filename)
           throws FunctionApproximatorException,
                  java.io.IOException

Loads the definition of a Bilinear2D function approximator from a file.

Parameters:

filename - the file name.

Throws:

java.io.IOException - if an I/O error occurs.

FunctionApproximatorException - if a parse error occurs.

See Also:

FunctionApproximator

Method Detail

saveDefinition

public void saveDefinition(java.lang.String filename)
                    throws FunctionApproximatorException,
                           java.io.IOException

Save a definition of this instance in a file.

Overrides:

saveDefinition in class FunctionApproximator

Parameters:

filename - the file name.

Throws:

java.io.IOException - if an I/O error occurs.

FunctionApproximatorException - if something wrong occurs.

query

public double[] query(double[] point)

Computes and returns the bilinear interpolation associated with the point. The point is clipped to the domain rectangle.

Overrides:

query in class FunctionApproximator

Parameters:

point - the input point (two-dimensional array of doubles).

Returns:

the output point (two-dimensional array of doubles).

query

public double[] query(int x,
                      int y)

Computes and returns the bilinear interpolation associated with the point. The point is clipped to the domain rectangle.

Parameters:

x - the x ordinate of the input point.

y - the y ordinate of the input point.

Returns:

the output point (two-dimensional array of doubles).

update

public void update(double[] q,
                   double[] p)
            throws FunctionApproximatorException

Not implemented.

Overrides:

update in class FunctionApproximator

Throws:

FunctionApproximatorException - always.