On Wed, Jun 20, 2012 at 3:58 PM, Neal Becker <ndbecker2 at gmail.com> wrote: > Maybe I'm being slow, but is there any convenient function to calculate, > for 2 vectors: > > \sum_i \sum_j x_i y_j > > (I had a matrix once, but it vanished without a trace) np.multiply.outer(x, y).sum() -- Robert Kern