[SciPy-dev] Scipy cannot handle singular eigenvalue problems

Nils Wagner wagner.nils at vdi.de
Wed Dec 10 16:49:38 CST 2003


------------------- 
 
 
On Wed, 10 Dec 2003, Nils Wagner wrote: 
 
> Scipy cannot handle singular eigenvalue problems. Note, that both 
> matrices 
> are singular. 
>  
> from scipy import * 
> A = array(([1.,-1.],[-1.,1.])) 
> B = array(([1.0,0.0],[0.0,0.0])) 
> w,vr = linalg.eig(A,B) 
> print w 
> print vr 
>  
> Traceback (most recent call last): 
<snip> 
> ValueError: matrices are not aligned for copy 
 
This issue is now resolved in CVS. Thanks Travis! 
 
Pearu 
 
It seems to be resolved. However, a second example  
doesn't work. 
>>> A 
array([[ 1.,  0.], 
       [ 0.,  0.]]) 
>>> B 
array([[ 1.,  0.], 
       [ 0.,  0.]]) 
>>> w,vr = linalg.eig(A,B) 
Traceback (most recent call last): 
  File "<stdin>", line 1, in ? 
  File "/usr/local/lib/python2.3/site-packages/scipy/linalg/decomp.py", line 
109, in eig 
    return _geneig(a1,b,left,right,overwrite_a,overwrite_b) 
  File "/usr/local/lib/python2.3/site-packages/scipy/linalg/decomp.py", line 
68, in _geneig 
    vr = _make_complex_eigvecs(w, vr, t) 
  File "/usr/local/lib/python2.3/site-packages/scipy/linalg/decomp.py", line 
29, in _make_complex_eigvecs 
    vnew.real = scipy_base.take(vin,ind[::2],1) 
ValueError: matrices are not aligned for copy 
>>> 
Any comment ? 
 
Nils 
 
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