[Numpy-discussion] fixing diag() for matrices

Sven Schreiber svetosch at gmx.net
Tue Jul 25 11:45:22 CDT 2006


there was a thread about this before, diag() is currently only
partly useful if you work with numpy-matrices, because the 1d->2d
direction doesn't work, as there are no 1d-numpy-matrices. This is
unfortunate because a numpy-matrix with shape (n,1) or (1,m) should be
naturally treated as a vector, imho. So it would be nice if this could
be fixed.

It's probably not the most efficient solution, but what I want for
numpy-matrix input x is to get:


where diag is the current implementation. This means that if x is not a
vector ("truly 2d"), then nothing is changed. But if one of the
dimensions of x is ==1, then it's turned into a 1d-array, and diag works
as it should.

Does that sound reasonable?


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