Package com.imsl.math

Class Eigen

java.lang.Object
com.imsl.math.Eigen
public class Eigen extends Object
Collection of Eigen System functions.

Eigen computes the eigenvalues and eigenvectors of a real matrix. The matrix is first balanced. Orthogonal similarity transformations are used to reduce the balanced matrix to a real upper Hessenberg matrix. The implicit double-shifted QR algorithm is used to compute the eigenvalues and eigenvectors of this Hessenberg matrix. The eigenvectors are normalized such that each has Euclidean length of value one. The largest component is real and positive.

The balancing routine is based on the EISPACK routine BALANC. The reduction routine is based on the EISPACK routines ORTHES and ORTRAN. The QR algorithm routine is based on the EISPACK routine HQR2. See Smith et al. (1976) for the EISPACK routines. Further details, some timing data, and credits are given in Hanson et al. (1990).

While the exact value of the performance index, \(\tau\), is highly machine dependent, the performance of Eigen is considered excellent if \(\tau \lt 1\), good if \(1 \le \tau \le 100\), and poor if \( \tau \gt 100\).

The performance index was first developed by the EISPACK project at Argonne National Laboratory; see Smith et al. (1976, pages 124-125).

See Also:

  • Nested Class Summary

    Nested Classes
    Modifier and Type
    Class
    Description
    static class 
    Eigen.DidNotConvergeException
    The iteration did not converge

  • Constructor Summary

    Constructors
    Constructor
    Description
    Eigen()
    Constructs the eigenvalues and the eigenvectors of a real square matrix.
    Eigen(double[][] a)
    Deprecated.
    Use Eigen() instead.
    Eigen(double[][] a, boolean computeVectors)
    Deprecated.
    Use Eigen() instead.

  • Method Summary

    Modifier and Type
    Method
    Description
    int
    getMaxIterations()
    Returns the maximum number of iterations.
    Complex[]
    getValues()
    Returns the eigenvalues of a matrix of type double.
    Complex[][]
    getVectors()
    Returns the eigenvectors.
    double
    performanceIndex(double[][] a)
    Returns the performance index of a real eigensystem.
    void
    setMaxIterations(int maxIterations)
    Set the maximum number of iterations allowed.
    void
    solve(double[][] a, boolean computeVectors)
    Solves for the eigenvalues and (optionally) the eigenvectors of a real square matrix.

    Methods inherited from class java.lang.Object

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

  • Constructor Details

    • Eigen

      public Eigen()
      Constructs the eigenvalues and the eigenvectors of a real square matrix.

    • Eigen

      public Eigen(double[][] a) throws Eigen.DidNotConvergeException
      Deprecated.
      Use Eigen() instead.
      Constructs the eigenvalues and the eigenvectors of a real square matrix.
      Parameters:
      a - is the double square matrix whose eigensystem is to be constructed
      Throws:
      Eigen.DidNotConvergeException - is thrown when the algorithm fails to converge on the eigenvalues of the matrix.

    • Eigen

      public Eigen(double[][] a, boolean computeVectors) throws Eigen.DidNotConvergeException
      Deprecated.
      Use Eigen() instead.
      Constructs the eigenvalues and (optionally) the eigenvectors of a real square matrix.
      Parameters:
      a - is the double square matrix whose eigensystem is to be constructed
      computeVectors - is true if the eigenvectors are to be computed
      Throws:
      Eigen.DidNotConvergeException - is thrown when the algorithm fails to converge on the eigenvalues of the matrix.

  • Method Details

    • solve

      public void solve(double[][] a, boolean computeVectors) throws Eigen.DidNotConvergeException
      Solves for the eigenvalues and (optionally) the eigenvectors of a real square matrix.
      Parameters:
      a - is the double square matrix for which the eigenvalues and (optionally) eigenvectors are to be found
      computeVectors - is true if the eigenvectors are to be computed
      Throws:
      Eigen.DidNotConvergeException - is thrown when the algorithm fails to converge on the eigenvalues of the matrix.

    • setMaxIterations

      public void setMaxIterations(int maxIterations)
      Set the maximum number of iterations allowed.
      Parameters:
      maxIterations - an int specifying the maximum number of iterations allowed. maxIterations must be greater than 0. By default, maxIterations = 50.

    • getMaxIterations

      public int getMaxIterations()
      Returns the maximum number of iterations.
      Returns:
      an int containing the maximum number of iterations.

    • getValues

      public Complex[] getValues()
      Returns the eigenvalues of a matrix of type double.
      Returns:
      a Complex array containing the eigenvalues of this matrix in descending order

    • getVectors

      public Complex[][] getVectors()
      Returns the eigenvectors.
      Returns:
      A Complex matrix containing the eigenvectors. The eigenvector corresponding to the j-th eigenvalue is stored in the j-th column. Each vector is normalized to have Euclidean length one.

    • performanceIndex

      public double performanceIndex(double[][] a)
      Returns the performance index of a real eigensystem.
      Parameters:
      a - a double matrix
      Returns:
      A double scalar value indicating how well the algorithms which have computed the eigenvalue and eigenvector pairs have performed. A performance index less than 1 is considered excellent, 1 to 100 is good, while greater than 100 is considered poor.