com.imsl.stat
Class Dissimilarities

java.lang.Object
  com.imsl.stat.Dissimilarities

All Implemented Interfaces:

Serializable, Cloneable

public class Dissimilarities
extends Object
implements Serializable, Cloneable

Computes a matrix of dissimilarities (or similarities) between the columns (or rows) of a matrix.

Class Dissimilarities computes an upper triangular matrix (excluding the diagonal) of dissimilarities (or similarities) between the columns (or rows) of a matrix. Nine different distance measures can be computed. For the first three measures, three different scaling options can be employed. The distance matrix computed is generally used as input to clustering or multidimensional scaling functions.

The following discussion assumes that the distance measure is being computed between the columns of the matrix. If distances between the rows of the matrix are desired, use row = true in the setRow method.

The distance method and scaling option used by Dissimilarities can be set via methods setDistanceMethod and setScalingOption, respectively. For distance methods L2_NORM, L1_NORM, or INFINITY_NORM, each row of x is first scaled according to the value specified by the setScalingOption method. The scaling parameters are obtained from the values in the row scaled as either the standard deviation of the row or the row range; the standard deviation is computed from the unbiased estimate of the variance. If no scaling is performed, the parameters in the following discussion are all 1.0 (see setScalingOption). Once the scaling value (if any) has been computed, the distance between column i and column j is computed via the difference vector , where denotes the k-th element in the i-th column, denotes the corresponding element in the j-th column, and ndstm is the number of rows if differencing columns and the number of columns if differencing rows. For given , the distance methods that allow scaling are defined as:

distanceMethod	Metric
L2_NORM	Euclidean distance ( norm)
L1_NORM	Sum of the absolute differences ( norm)
INFINITY_NORM	Maximum difference ( norm)

The following distance measures do not allow for scaling.

distanceMethod	Metric
MAHALANOBIS	Mahalanobis distance
ABS_COSINE	Absolute value of the cosine of the angle between the vectors
ANGLE_IN_RADIANS	Angle in radians (0, ) between the lines through the origin defined by the vectors
CORRELATION_COEFFICIENT	Correlation coefficient
ABS_CORRELATION_COEFFICIENT	Absolute value of the correlation coefficient
EXACT_MATCHES	Number of exact matches, where .

For the Mahalanobis distance, any variable used in computing the distance measure that is (numerically) linearly dependent upon the previous variables in the indexArray vector from the setIndex method is omitted from the distance measure.

See Also:

Example 1, Example 2, Serialized Form

Nested Class Summary

static class	Dissimilarities.NoPositiveVarianceException No variable has positive variance.
static class	Dissimilarities.ScaleFactorZeroException The computations cannot continue because a scale factor is zero.
static class	Dissimilarities.ZeroNormException The computations cannot continue because the Euclidean norm of the column is equal to zero.

Field Summary

static int	ABS_CORRELATION_COEFFICIENT Indicates the absolute value of the correlation coefficient distance method.
static int	ABS_COSINE Indicates the absolute value of the cosine of the angle between the vectors distance method.
static int	ANGLE_IN_RADIANS Indicates the angle in radians (0, ) between the lines through the origin defined by the vectors distance method.
static int	CORRELATION_COEFFICIENT Indicates the correlation coefficient distance method.
static int	EXACT_MATCHES Indicates the number of exact matches distance method.
static int	INFINITY_NORM Indicates the maximum difference ( norm) distance method.
static int	L1_NORM Indicates the sum of the absolute differences ( norm) distance method.
static int	L2_NORM Indicates the Euclidean distance method ( norm).
static int	MAHALANOBIS Indicates the Mahalanobis distance method.
static int	NO_SCALING Indicates no scaling.
static int	RANGE Indicates scaling by the range.
static int	STD_DEV Indicates scaling by the standard deviation.

Constructor Summary

Dissimilarities(double[][] x)
Constructor for Dissimilarities.

Method Summary

void	compute() Computes a matrix of dissimilarities (or similarities) between the columns (or rows) of a matrix.
double[][]	getDistanceMatrix() Returns the distance matrix.
int	getDistanceMethod() Returns the method used in computing the dissimilarities or similarities.
int[]	getIndex() Returns the indices of the rows (columns) used in computing the distance measure.
boolean	getRow() Returns a boolean indicating whether distances are computed between rows or columns of x.
int	getScalingOption() Returns the scaling option.
void	setDistanceMethod(int distanceMethod) Sets the method to be used in computing the dissimilarities or similarities.
void	setIndex(int[] indexArray) Sets the indices of the rows (columns).
void	setRow(boolean row) Identifies whether distances are computed between rows or columns of x.
void	setScalingOption(int distanceScale) Sets the scaling option used if the L2_NORM, L1_NORM, or INFINITY_NORM distance methods are specified.

Methods inherited from class java.lang.Object

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

Field Detail

ABS_CORRELATION_COEFFICIENT

public static final int ABS_CORRELATION_COEFFICIENT

Indicates the absolute value of the correlation coefficient distance method.

See Also:

Constant Field Values

ABS_COSINE

public static final int ABS_COSINE

Indicates the absolute value of the cosine of the angle between the vectors distance method.

See Also:

Constant Field Values

ANGLE_IN_RADIANS

public static final int ANGLE_IN_RADIANS

Indicates the angle in radians (0, ) between the lines through the origin defined by the vectors distance method.

See Also:

Constant Field Values

CORRELATION_COEFFICIENT

public static final int CORRELATION_COEFFICIENT

Indicates the correlation coefficient distance method.

See Also:

Constant Field Values

EXACT_MATCHES

public static final int EXACT_MATCHES

Indicates the number of exact matches distance method.

See Also:

Constant Field Values

INFINITY_NORM

public static final int INFINITY_NORM

Indicates the maximum difference ( norm) distance method.

See Also:

Constant Field Values

L1_NORM

public static final int L1_NORM

Indicates the sum of the absolute differences ( norm) distance method.

See Also:

Constant Field Values

L2_NORM

public static final int L2_NORM

Indicates the Euclidean distance method ( norm).

See Also:

Constant Field Values

MAHALANOBIS

public static final int MAHALANOBIS

Indicates the Mahalanobis distance method.

See Also:

Constant Field Values

NO_SCALING

public static final int NO_SCALING

Indicates no scaling.

See Also:

Constant Field Values

RANGE

public static final int RANGE

Indicates scaling by the range.

See Also:

Constant Field Values

STD_DEV

public static final int STD_DEV

Indicates scaling by the standard deviation.

See Also:

Constant Field Values

Constructor Detail

Dissimilarities

public Dissimilarities(double[][] x)

Constructor for Dissimilarities.

Parameters:

x - A double matrix containing the data input matrix.

Method Detail

compute

public void compute()
             throws Dissimilarities.ScaleFactorZeroException,
                    Dissimilarities.ZeroNormException,
                    Dissimilarities.NoPositiveVarianceException

Computes a matrix of dissimilarities (or similarities) between the columns (or rows) of a matrix.

Throws:

Dissimilarities.ScaleFactorZeroException - is thrown when computations cannot continue because a scale factor is zero

Dissimilarities.NoPositiveVarianceException - is thrown when no variable has positive variance

Dissimilarities.ZeroNormException - is thrown when the Euclidean norm of a column is equal to zero

getDistanceMatrix

public final double[][] getDistanceMatrix()

Returns the distance matrix.

Returns:

A double matrix containing the distance matrix.

getDistanceMethod

public int getDistanceMethod()

Returns the method used in computing the dissimilarities or similarities.

getIndex

public int[] getIndex()

Returns the indices of the rows (columns) used in computing the distance measure.

getRow

public boolean getRow()

Returns a boolean indicating whether distances are computed between rows or columns of x.

getScalingOption

public int getScalingOption()

Returns the scaling option.

setDistanceMethod

public void setDistanceMethod(int distanceMethod)

Sets the method to be used in computing the dissimilarities or similarities.

Parameters:

distanceMethod - An int identifying the method to be used in computing the dissimilarities or similarities. Acceptable values of distanceMethod are:

distanceMethod	Metric
L2_NORM	Euclidean distance ( norm)
L1_NORM	Sum of the absolute differences ( norm)
INFINITY_NORM	Maximum difference ( norm)
MAHALANOBIS	Mahalanobis distance
ABS_COSINE	Absolute value of the cosine of the angle between the vectors
ANGLE_IN_RADIANS	Angle in radians (0, ) between the lines through the origin defined by the vectors
CORRELATION_COEFFICIENT	Correlation coefficient
ABS_CORRELATION_COEFFICIENT	Absolute value of the correlation coefficient
EXACT_MATCHES	Number of exact matches, where .

See class description for more details. By default, distanceMethod = L2_NORM.

setIndex

public void setIndex(int[] indexArray)

Sets the indices of the rows (columns).

Parameters:

indexArray - An int array containing the indices of the columns (rows if row = false) to be used in computing the distance measure. By default, if row = true, indexArray = 0, 1, ..., x[0].length-1. If row = false, indexArray = 0, 1, ..., x.length-1, see setRow.

setRow

public void setRow(boolean row)

Identifies whether distances are computed between rows or columns of x.

Parameters:

row - A boolean identifying whether distances are computed between rows or columns of x. If row = true, distances are computed between the rows of x. Otherwise, distances between the columns of x are computed. By default, row = true.

setScalingOption

public void setScalingOption(int distanceScale)

Sets the scaling option used if the L2_NORM, L1_NORM, or INFINITY_NORM distance methods are specified. See setDistanceMethod.

Parameters:

distanceScale - An int containing the scaling option. By default, distanceScale = NO_SCALING.

distanceScale	Method
NO_SCALING	No scaling is performed.
STD_DEV	If setRow(false), scale each column by the standard deviation of the column. If setRow(true), scale each row by the standard deviation of the row.
RANGE	If setRow(false), scale each column by the range of the column. If setRow(true), scale each row by the range of the row.