On Sun, 26 Apr 2015, John Cremona wrote:
Is there a good definition of the rank of matrix over a ring which is not an integral domain? What is the rank of the 1x1 matrix (2) over Z/4Z, for example?
Hmm... good question. I was just thinking linear dependency (is row n equal to e_1*r_1+...+e_{n-1}*r_{n-1}, where r_i is a row and e_i is an element of the ring). But this should be modified if we want full rank to mean invertible matrix.
But if rank is not defined then Sage should not raise NotImplemented but ValueError.
-- Jori Mäntysalo
