OrderedEigenDecomposition - other eigenvalue sort options?

[axelclk]

Hi

Is it possible to add an option so that eigenvalues are sorted in descending order of complex absolute value in OrderedComplexEigenDecomposition:

• https://github.com/Hipparchus-Math/hipparchus/blob/master/hipparchus-core/src/main/java/org/hipparchus/linear/OrderedComplexEigenDecomposition.java

  public static void main(String[] args) {
    double[][] d = {{-8.0, 12.0, 4.0}, {12.0, -20.0, 0.0}, {4.0, 0.0, -2.0}};
    Array2DRowRealMatrix matrix = new Array2DRowRealMatrix(d);
    ComplexEigenDecomposition ed = new OrderedComplexEigenDecomposition(matrix);
    Complex[] realValues = ed.getEigenvalues(); 
    for (int i = 0; i < realValues.length; i++) {
      System.out.print(realValues[i]);
      System.out.print(", ");
    } 
  }
  

The next example gets an exception:

Exception in thread "main" java.lang.NullPointerException
at org.hipparchus.linear.OrderedComplexEigenDecomposition.<init>(OrderedComplexEigenDecomposition.java:56)



  public static void main(String[] args) {
    double[][] d = {{1.0, 0.0, 0.0}, {0.0, 1.0, 0.0}, {0.0, 0.0, 1.0}};
    Array2DRowRealMatrix matrix = new Array2DRowRealMatrix(d);
    ComplexEigenDecomposition ed = new OrderedComplexEigenDecomposition(matrix);
    Complex[] realValues = ed.getEigenvalues(); 
    for (int i = 0; i < realValues.length; i++) {
      System.out.print(realValues[i]);
      System.out.print(", ");
    } 
  }