weka.core.matrix

## Class EigenvalueDecomposition

- java.lang.Object
- - weka.core.matrix.EigenvalueDecomposition

- All Implemented Interfaces:
    java.io.Serializable, RevisionHandler

      public class EigenvalueDecomposition
      extends java.lang.Object
      implements java.io.Serializable, RevisionHandler

  Eigenvalues and eigenvectors of a real matrix.

  If A is symmetric, then A = V*D*V' where the eigenvalue matrix D is diagonal and the eigenvector matrix V is orthogonal. I.e. A = V.times(D.times(V.transpose())) and V.times(V.transpose()) equals the identity matrix.

  If A is not symmetric, then the eigenvalue matrix D is block diagonal with the real eigenvalues in 1-by-1 blocks and any complex eigenvalues, lambda + i*mu, in 2-by-2 blocks, [lambda, mu; -mu, lambda]. The columns of V represent the eigenvectors in the sense that A*V = V*D, i.e. A.times(V) equals V.times(D). The matrix V may be badly conditioned, or even singular, so the validity of the equation A = V*D*inverse(V) depends upon V.cond().

  Adapted from the JAMA package.
  Version:
    $Revision: 5953 $
  Author:
    The Mathworks and NIST, Fracpete (fracpete at waikato dot ac dot nz)
  See Also:
    Serialized Form

- - ### Constructor Summary

    Constructors
    Constructor and Description
    `EigenvalueDecomposition(Matrix Arg)` Check for symmetry, then construct the eigenvalue decomposition

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `Matrix` | `getD()` Return the block diagonal eigenvalue matrix
    `double[]` | `getImagEigenvalues()` Return the imaginary parts of the eigenvalues
    `double[]` | `getRealEigenvalues()` Return the real parts of the eigenvalues
    `java.lang.String` | `getRevision()` Returns the revision string.
    `Matrix` | `getV()` Return the eigenvector matrix

    - ### Methods inherited from class java.lang.Object

      `equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Constructor Detail

    - #### EigenvalueDecomposition

          public EigenvalueDecomposition(Matrix Arg)

      Check for symmetry, then construct the eigenvalue decomposition
      Parameters:
        `Arg` - Square matrix

  - ### Method Detail

    - #### getV

          public Matrix getV()

      Return the eigenvector matrix
      Returns:
        V

    - #### getRealEigenvalues

          public double[] getRealEigenvalues()

      Return the real parts of the eigenvalues
      Returns:
        real(diag(D))

    - #### getImagEigenvalues

          public double[] getImagEigenvalues()

      Return the imaginary parts of the eigenvalues
      Returns:
        imag(diag(D))

    - #### getD

          public Matrix getD()

      Return the block diagonal eigenvalue matrix
      Returns:
        D

    - #### getRevision

          public java.lang.String getRevision()

      Returns the revision string.
      Specified by:
        `getRevision` in interface `RevisionHandler`
      Returns:
        the revision