Eigenvalues of sparse arrays
- To: mathgroup at smc.vnet.net
- Subject: [mg102154] Eigenvalues of sparse arrays
- From: gopher <gophergoon at gmail.com>
- Date: Fri, 31 Jul 2009 05:52:59 -0400 (EDT)
I am computing the eigenvalues of a matrix 's'.
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In[164]:= SparseArray[s] == s
Out[164]= True
In[165]:= Eigenvalues[s, -6] // Chop
Out[165]= {0.382326, -0.382326, 0.350062, -0.350062, 0, 0}
In[166]:= Eigenvalues[SparseArray[s], -6] // Chop
Out[166]= {0.38245, -0.352447, 0.351011, 1.26736*10^-7, 0, 0}
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Why are the two results different? Is there an issue with precision
when computing eigenvalues of sparse arrays? The matrix is such that
the eigenvalues are symmetric about 0 so I'm pretty sure that the
first result is correct.