Real inner-product in python
Chad Netzer
cnetzer at mail.arc.nasa.gov
Wed Jan 22 04:46:18 CET 2003
On Saturday 18 January 2003 22:56, Nadav Horesh wrote:
> Is there a package/routine that implements inner-product for arrays
> with rank>2?
> I read in an old thread (1995) a thought to implement an APL-like dot
> (.) operator in Numeric package (add.inner.subtract <=> +.-) does
> anyone know about an implementation of the idea?
Numeric does have dot(), and it may do exactly what you want. Here's
an example with 1, 2, and 3 dimensional arrays:
$ python
Python 2.2.2 (#1, Jan 3 2003, 12:42:27)
>>> import Numeric as Num
>>> a = Num.array( [1,2,3] )
>>> b = Num.array( [a, a+3,a+6])
>>> c = Num.array( [b, b+10, b+20] )
>>> Num.rank(a)
1
>>> Num.rank(b)
2
>>> Num.rank(c)
3
>>> Num.dot(a,a)
14
>>> Num.dot(b,a)
array([14, 32, 50])
>>> Num.dot(a,b)
array([30, 36, 42])
>>> Num.dot(b,b)
array([[ 30, 36, 42],
[ 66, 81, 96],
[102, 126, 150]])
>>> Num.dot(c,a)
array([[ 14, 32, 50],
[ 74, 92, 110],
[134, 152, 170]])
>>> Num.dot(a,c)
array([[30, 36, 42],
[51, 57, 63],
[71, 77, 83]])
>>> Num.dot(c,b)
array([[[ 30, 36, 42],
[ 66, 81, 96],
[102, 126, 150]],
[[150, 186, 222],
[186, 231, 276],
[222, 276, 330]],
[[270, 336, 402],
[306, 381, 456],
[342, 426, 510]]])
>>> Num.dot(b,c)
array([[[ 30, 36, 42],
[ 51, 57, 63],
[ 71, 77, 83]],
[[ 66, 81, 96],
[117, 132, 147],
[167, 182, 197]],
[[102, 126, 150],
[183, 207, 231],
[263, 287, 311]]])
etc...
Is that all you need?
>
> Nadav.
--
Bay Area Python Interest Group - http://www.baypiggies.net/
Chad Netzer
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