[SciPy-user] Dot in greater than 2D
Brian Lewis
brian.lewis17 at gmail.com
Mon Jun 15 13:52:51 EDT 2009
How is dot defined for matrices with dimension greater than 2? The
docstring says:
dot(a,b)
Returns the dot product of a and b for arrays of floating point types.
Like the generic numpy equivalent the product sum is over
the last dimension of a and the second-to-last dimension of b.
NB: The first argument is not conjugated.
which seemed a bit cryptic to me. Is there any documentation on this with
an example using arrays with greater than 2 dimensions? On first read, it
seemed like only the summed dimensions needed to agree. So,
a.shape == (5,3,2)
b.shape == (10,2,20)
but I get that the objects are not aligned. On second read, it seemed like
maybe dot would apply itself recursively. So maybe
a.shape == (5,3,2)
b.shape == (3,2,5)
would work since a[:,:,i] has shape (5,3) and is compatible (via dot) with
b[:,i,:] whose shape is (3,5). Not so surprisingly, the objects are also not
aligned.
Apologies for my naivety.
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