[Numpy-discussion] broadcasting question

Robert Kern robert.kern@gmail....
Thu Aug 30 07:21:16 CDT 2012


On Thu, Aug 30, 2012 at 12:49 PM, Neal Becker <ndbecker2@gmail.com> wrote:
> I think this should be simple, but I'm drawing a blank
>
> I have 2 2d matrixes
>
> Matrix A has indexes (i, symbol)
> Matrix B has indexes (state, symbol)
>
> I combined them into a 3d matrix:
>
> C = A[:,newaxis,:] + B[newaxis,:,:]
> where C has indexes (i, state, symbol)
>
> That works fine.
>
> Now suppose I want to omit B (for debug), like:
>
> C = A[:,newaxis,:]
>
> In other words, all I want is to add a dimension into A and force it to
> broadcast along that axis.  How do I do that?

C, dummy = numpy.broadcast_arrays(A[:,newaxis,:], numpy.empty([1,state,1]))

-- 
Robert Kern


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