On 18 October 2013 16:52, <chip9m...@gmail.com> wrote: > Interesting! > rank of the whole minus last row > numpy.linalg.matrix_rank(users_elements_matrix[:,0:42]) is 42 > > but also rank of whole is > numpy.linalg.matrix_rank(users_elements_matrix[:,0:43]) is 42 > > but what does that mean?!
It means that the additional column is a linear combination of the existing columns. This means that your system of equations can contain a contradiction. Essentially you're trying to get the least squares solution to something like: 3*x + y = 1 1*x + 2*y = 4 1*x + 2*y = 5 # Contradicts the equation above Because of floating point error it isn't *exactly* a contradiction so you get silly values instead of an error. > could you explain briefly what now? http://en.wikipedia.org/wiki/Rank_(linear_algebra) Oscar -- https://mail.python.org/mailman/listinfo/python-list
