com.aliasi.matrix
Class Matrices

java.lang.Object
  com.aliasi.matrix.Matrices

public class Matrices
extends Object

The Matrices class contains static utility methods for various matrix properties and operations.

Since:

LingPipe2.0

Version:

3.5

Author:

Bob Carpenter

Method Summary

static boolean	hasZeroDiagonal(Matrix m) Returns true if the specified matrix has only zero values on its diagonal.
static boolean	isNonNegative(Matrix m) Returns true if the matrix contains only positive numbers or zeros.
static boolean	isSymmetric(Matrix m) Returns true if the specified matrix is symmetric.
static double[]	toArray(Vector v) Returns the content of the specified vector as an array.
static Vector	unmodifiableVector(Vector v) Returns an unmodifiable view of the specified vector.

Methods inherited from class java.lang.Object

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

Method Detail

unmodifiableVector

public static Vector unmodifiableVector(Vector v)

Returns an unmodifiable view of the specified vector. This provides a "read-only" version of the specified vector. The returned vector is backed by the specified vector, so changes to the specified vector will be refelcted in the returned vector. An unmodifiable vector throws an UnsupportedOperationException if Vector.setValue(int,double) is called.

Parameters:

v - Vector to return an

hasZeroDiagonal

public static boolean hasZeroDiagonal(Matrix m)

Returns true if the specified matrix has only zero values on its diagonal. If the matrix is not square or has non-zero values on the diagonal, the return result is false.

Parameters:

m - Matrix to test.

Returns:

true if the matrix is square and has only zero values on its diagonal.

isSymmetric

public static boolean isSymmetric(Matrix m)

Returns true if the specified matrix is symmetric. A matrix m is symmetric if it's equal to its transpose, m = mT. Stated directly, a matrix m is symmetric if it has the same number of rows as columns:

m.numRows() == m.numColumns()

and meets the symmetry condition:

m.value(i,j) == m.value(j,i) for i,j < m.numRows().

Parameters:

m - Matrix to test.

Returns:

true if the matrix is symmetric.

isNonNegative

public static boolean isNonNegative(Matrix m)

Returns true if the matrix contains only positive numbers or zeros. If it contains a finite negative number, Double.NaN, or Double.NEGATIVE_INFINITY, the result will be false.

Parameters:

m - Matrix to test.

Returns:

true if the matrix contains only positive entries or zeros.

toArray

public static double[] toArray(Vector v)

Returns the content of the specified vector as an array.

Parameters:

v - The vector.

Returns:

The content of the vector as an array.