[SciPy-user] Mathematica Element-wise Multiplication

Stefan van der Walt stefan@sun.ac...
Sat Dec 15 05:31:42 CST 2007


Hi Tom

On Fri, Dec 14, 2007 at 09:26:59PM -0800, Tom Johnson wrote:
> While playing with Mathematica, I must say that I was surprised to
> find that it handled element-wise multiplication differently from
> scipy.
> 
> In scipy,
> 
> >>> A = array([[1,2],[3,4]])
> >>> B = array([2,3])
> >>> A * B
> array([[2,6],[6,12]])
> 
> which essentially multiplies each COLUMN of A with each COLUMN of B.

Numpy does what we call broadcasting.  You can read more about it at

http://www.scipy.org/EricsBroadcastingDoc

If you'd like to have the Mathematica behaviour, you can always use
the transpose property (i.e. x.T).

Regards
Stéfan


More information about the SciPy-user mailing list