[SciPy-user] Trace of a sparse matrix ?

Nils Wagner nwagner at mecha.uni-stuttgart.de
Thu Feb 16 10:43:08 CST 2006

Arnd Baecker wrote:
>On Thu, 16 Feb 2006, Nils Wagner wrote:
>>Hi all,
>>Is it possible to compute the trace of a sparse matrix say A
>>without detouring
>>spur=trace(A.todense()) ?
>what about summing up all diagonal elements which exist in A?
and are not equal to zero.

It would be nice to have a built-in function "sptrace(A)" for this task
within scipy :-)

The same holds for the norm of a sparse matrix


linalg.norm(A.todense()) is not optimal or even impossible if A is
really large.


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