[Numpy-discussion] Some questions about dot()

[Alan G Isaac]

On Mon, 1 May 2006, Bill Baxter apparently wrote: 
> Seems like it would make more sense to have dot() follow 
> the mathematical convention of a.T * b, and have 
> a separate function, like mult() or matrixmult(),  do what 
> dot() does currently.  Is there historical baggage of some 
> kind here preventing that?  Or some maybe there's 
> a different definition of dot product from another branch 
> of mathematics that I'm not familiar with? 

Historically, 'dot' was essentially an alias for 
'multiarray.matrixproduct' in Numeric.  This is a long 
standing use that I would not expect to change.  (But I am 
just a user.)

I believe you have found a documentation bug, as 
matrixproduct either no longer exists or is well hidden.

On the more general point ...

Can you point to a definition that matches your proposed 
use?  The most common definition I know for 'dot' is between 
vectors, which do not "transpose". In numpy this is 'vdot',
which returns a scalar product.

The production of a dot product between two column vectors 
in a linear algebra context by transposing and then matrix 
multiplying is, I believe, a convenience rather than 
a definition of any sort.  If we care about the details,
the result is also not a scalar.

Cheers,
Alan Isaac