org.esa.snap.core.util.math

Class LinearAlgebra

java.lang.Object

org.esa.snap.core.util.math.LinearAlgebra

public class LinearAlgebra
extends Object

Linear algebra - calculations and utilities for vectors and matrixes.

Note that for the purpose of performance the calculation functions do no argument checking.

Version:

$Revision$ $Date$

Constructor Summary

Constructors

Constructor and Description
LinearAlgebra()

Method Summary

Modifier and Type	Method and Description
static double	innerProduct(double[][] a, double[][] b, int i, int j) Calculates the inner product of a row in a matrix and a column in another matrix.
static double	innerProduct(double[] a, double[] b) Returns the inner product of two vectors.
static double	innerProduct(double[] a, double[][] b, int j) Calculates the inner product of a vector and a column in a matrix.
static boolean	isMatrix(double[][] array) Tests if a given double[][] array is a matrix.
static boolean	isMatrix(int rowCount, int colCount, double[][] array) Tests if a given double[][] array is a matrix with a prescribed number of rows and columns.
static double[]	multiply(double[][] a, double[] b) Multiplies a matrix by a vector (from the right).
static double[][]	multiply(double[][] a, double[][] b) Multiplies two matrixes.
static double[][]	multiply(double[][] a, double[][] b, double[][] c) Multiplies two matrixes.
static double[]	multiply(double[][] a, double[] b, double[] c) Multiplies a matrix by a vector (from the right).
static double[]	multiply(double[] b, double c) Multiplies a vector by a scalar.
static double[]	multiply(double[] b, double[][] a) Multiplies a matrix by a vector (from the left).
static double[]	multiply(double[] b, double[][] a, double[] c) Multiplies a matrix by a vector (from the left).
static double[]	multiplyAndSubtract(double[] b, double[][] a, double s) Multiplies a matrix by a vector (from the left) and subtracts a scalar.
static double[]	multiplyAndSubtract(double[] b, double[][] a, double s, double[] c) Multiplies a matrix by a vector (from the left) and subtracts a scalar.
static double[][]	outerProduct(double[] a, double[] b) Returns the outer product of two vectors.
static double[][]	outerProduct(double[] a, double[] b, double[][] c) Returns the outer product of two vectors.
static double[][]	subtract(double[][] a, double[] b, double[] c) Subtracts the outer product of two vectors from a matrix.

Methods inherited from class java.lang.Object

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

Constructor Detail

LinearAlgebra

public LinearAlgebra()

Method Detail

isMatrix

public static boolean isMatrix(double[][] array)

Tests if a given double[][] array is a matrix.

Parameters:

array - the array.

Returns:

true if the given array is a matrix, false otherwise.

isMatrix

public static boolean isMatrix(int rowCount,
                               int colCount,
                               double[][] array)

Tests if a given double[][] array is a matrix with a prescribed number of rows and columns.

Parameters:

rowCount - the prescribed number of rows. If zero or negative, any number of rows is accepted.

colCount - the prescribed number of columns. If zero or negative, any number of columns is accepted.

array - the array.

Returns:

true if the given array is a matrix, false otherwise.

multiply

public static double[] multiply(double[] b,
                                double c)

Multiplies a vector by a scalar.

Parameters:

b - the vector to be multiplied. On return contains the result.

c - the scalar.

Returns:

the result vector.

multiply

public static double[] multiply(double[][] a,
                                double[] b)

Multiplies a matrix by a vector (from the right).

Parameters:

a - the matrix.

b - the vector.

Returns:

the result vector.

multiply

public static double[] multiply(double[][] a,
                                double[] b,
                                double[] c)

Multiplies a matrix by a vector (from the right).

Parameters:

a - the matrix.

b - the vector.

c - the result vector.

Returns:

the result vector.

multiply

public static double[] multiply(double[] b,
                                double[][] a)

Multiplies a matrix by a vector (from the left).

Parameters:

b - the vector.

a - the matrix.

Returns:

the result vector.

multiply

public static double[] multiply(double[] b,
                                double[][] a,
                                double[] c)

Multiplies a matrix by a vector (from the left).

Parameters:

b - the vector.

a - the matrix.

c - the result vector.

Returns:

the result vector.

multiplyAndSubtract

public static double[] multiplyAndSubtract(double[] b,
                                           double[][] a,
                                           double s)

Multiplies a matrix by a vector (from the left) and subtracts a scalar.

Parameters:

b - the vector.

a - the matrix.

s - the scalar.

Returns:

the result vector.

multiplyAndSubtract

public static double[] multiplyAndSubtract(double[] b,
                                           double[][] a,
                                           double s,
                                           double[] c)

Multiplies a matrix by a vector (from the left) and subtracts a scalar.

Parameters:

b - the vector.

a - the matrix.

s - the scalar.

c - the result vector.

Returns:

the result vector.

innerProduct

public static double innerProduct(double[] a,
                                  double[] b)

Returns the inner product of two vectors.

Parameters:

a - the first vector.

b - the second vector.

Returns:

the inner product.

innerProduct

public static double innerProduct(double[] a,
                                  double[][] b,
                                  int j)

Calculates the inner product of a vector and a column in a matrix.

Parameters:

a - the vector.

b - the matrix.

j - the index of a column in b.

Returns:

the inner product of a and the ith column in b.

innerProduct

public static double innerProduct(double[][] a,
                                  double[][] b,
                                  int i,
                                  int j)

Calculates the inner product of a row in a matrix and a column in another matrix.

Parameters:

a - the first matrix.

b - the second matrix.

i - the index of a row in a.

j - the index of a column in b.

Returns:

the inner product of the ith row in a and the jth column in b.

outerProduct

public static double[][] outerProduct(double[] a,
                                      double[] b)

Returns the outer product of two vectors.

Parameters:

a - the first vector.

b - the second vector.

Returns:

the outer product.

outerProduct

public static double[][] outerProduct(double[] a,
                                      double[] b,
                                      double[][] c)

Returns the outer product of two vectors.

Parameters:

a - the first vector.

b - the second vector.

c - the result vector.

Returns:

the result vector.

multiply

public static double[][] multiply(double[][] a,
                                  double[][] b)

Multiplies two matrixes.

Parameters:

a - the first matrix.

b - the second matrix.

Returns:

the result matrix.

multiply

public static double[][] multiply(double[][] a,
                                  double[][] b,
                                  double[][] c)

Multiplies two matrixes.

Parameters:

a - the first matrix.

b - the second matrix.

c - the result matrix.

Returns:

the result matrix.

subtract

public static double[][] subtract(double[][] a,
                                  double[] b,
                                  double[] c)

Subtracts the outer product of two vectors from a matrix.

Parameters:

a - the matrix. On return contains the result matrix.

b - the first vector.

c - the second vector.

Returns:

the result matrix.