Package 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.

Constructor Summary

Constructors

Constructor	Description
LinearAlgebra()

Method Summary

Modifier and Type	Method	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.