On Sat, Mar 15, 2014 at 1:29 PM, Nathaniel Smith <n...@pobox.com> wrote:
> On 15 Mar 2014 19:02, "Charles R Harris" <charlesr.har...@gmail.com> > wrote: > > Just to throw something new into the mix > > > > u@v@w = u@(v@w) -- u@v is a dyadic matrix > > > > u@v -- is a scalar > > > > It would be nice if u@v@None, or some such, would evaluate as a dyad. > Or else we will still need the concept of row and column 1-D matrices. I > still think v.T should set a flag so that one can distinguish u@v.T(dyad) > from u.T@v(inner product), where 1-D arrays are normally treated as column > vectors. > > This sounds important but I have no idea what any of it means :-) (What's > a dyadic matrix?) Can you elaborate? > Dyadic matrices date back to the beginning of vector calculus and J. W. Gibbs. These days they are usually written as v*w.T, i.e., the outer product of two vectors and are a fairly common occurrence in matrix expressions. For instance, covariance matrices are defined as E(v * v.T) Chuck
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