[Octave-bug-tracker] [bug #45511] eig() sometimes accepts second matrix without using it

[anonymous]

URL:
  <http://savannah.gnu.org/bugs/?45511>

                 Summary: eig() sometimes accepts second matrix without using
it
                 Project: GNU Octave
            Submitted by: None
            Submitted on: Thu 09 Jul 2015 09:21:51 PM UTC
                Category: Octave Function
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Matlab Compatibility
                  Status: None
             Assigned to: None
         Originator Name: 
        Originator Email: address@hidden
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 3.8.2
        Operating System: Mac OS

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Details:

Sometimes, [V,D]=eig(K,M) solves the generalized eigenvalue equation lambda *
M * v = K * v, but other times it doesn't. 

For example, for K = [1 2; 3 4], M = [5 6; 7 8] it seems to work, and we get
two different answers for eig(K) vs. eig(K,M). 

However, for 
K = 
1.8000 + 0.0000i  -1.0970 + 0.9550i
  -1.0970 - 0.9550i   1.8000 + 0.0000i
and
M = 
209     0
     0   209
eig(K,M) gives the same answer as eig(K), which is incorrect. 

(I also posted the issue here:
http://stackoverflow.com/questions/31327630/scipy-linalg-eig-giving-different-eigenvectors-from-gnu-octaves-eig.)




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