[Octave-bug-tracker] [bug #66049] add cluster ordering to ordqz

[Anders Helmersson]

URL:
  <https://savannah.gnu.org/bugs/?66049>

                 Summary: add cluster ordering to ordqz
                   Group: GNU Octave
               Submitter: ahelmersson
               Submitted: Wed 31 Jul 2024 03:07:59 PM UTC
                Category: Octave Function
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Feature Request
                  Status: None
             Assigned to: None
         Originator Name: Anders Helmersson
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: stable
        Operating System: Any
           Fixed Release: None
         Planned Release: None


    _______________________________________________________

Follow-up Comments:


-------------------------------------------------------
Date: Wed 31 Jul 2024 03:07:59 PM UTC By: Anders Helmersson <ahelmersson>
The function "ordqz" can be called with a logical select vector to order the
the corresponding eigenvalues up front, in the example below it moves the 1st,
4th and 5th eigenvalue to the left.

>> select = [1 0 0 1 1 0];
>> [ar, br, qr, zr] = ordqz (aa, bb, q, z, select)

In Matlab, it is possible to order the eigenvalues in clusters. For instance,
in the example below, it moves the 1st, 4th and 5th eigenvalue to the left
followed by the 6th eigenvalue and then the remaining ones.

>> cluster = [1 3 3 1 1 2];
>> [ar, br, qr, zr] = ordqz (aa, bb, q, z, cluster)

It seems possible to achieve this by calling ordqz several times using
appropriate logical select vectors, but this assumes that unaffected
eigenvalues are not moved during the call. However, this is not documented, so
it cannot be relied upon.

>> [ar, br, qr, zr] = ordqz (aa, bb, q, z, [1 0 0 1 1 0])
>> [arr, brr, qrr, zrr] = ordqz (ar, br, qr, zr, [1 1 1 0 0 1])

Using the proposed cluster feature, would make it possible to group
eigenvalues in a flexible way.







    _______________________________________________________

Reply to this item at:

  <https://savannah.gnu.org/bugs/?66049>

_______________________________________________
Message sent via Savannah
https://savannah.gnu.org/

signature.asc
Description: PGP signature