python - Calculate Matrix Rank using scipy

Question

I'd like to calculate the mathematical rank of a matrix using scipy. The most obvious function numpy.rank calculates the dimension of an array (ie. scalars have dimension 0, vectors 1, matrices 2, etc...). I am aware that the numpy.linalg.lstsq module has this capability, but I was wondering if such a fundamental operation is built into the matrix class somewhere.

Here is an explicit example:

from numpy import matrix, rank
A = matrix([[1,3,7],[2,8,3],[7,8,1]])
print rank(A)

This gives 2 the dimension, where I'm looking for an answer of 3.

Answer 1

Numpy provides numpy.linalg.matrix_rank():

>>> import numpy
>>> numpy.__version__
'1.5.1'
>>> A = numpy.matrix([[1,3,7],[2,8,3],[7,8,1]])
>>> numpy.linalg.matrix_rank(A)
3