On Tue, 30 Jun 2009 11:22:34 +0200
"Nils Wagner" <nwag...@iam.uni-stuttgart.de> wrote:
Hi all,
How can I build the following product with numpy
q_i = \varepsilon_{ijk} q_{kj}
where \varepsilon_{ijk} denotes the permutation symbol.
Nils
Sorry for replying to myself.
The permutation symbol is also known as the Levi-Civita
symbol.
I found an explicit expression at
http://en.wikipedia.org/wiki/Levi-Civita_symbol
How do I build the product of the Levi-Civita symbol
\varepsilon_{ijk} and the two dimensional array
q_{kj}, i,j,k = 1,2,3 ?
Nils
from numpy import zeros
def levi_civita():
""" Levi-Civita symbol
http://en.wikipedia.org/wiki/Levi-Civita_symbol
"""
eps = zeros((3,3,3),float)
for i in range(1,4):
for j in range(1,4):
for k in range(1,4):
eps[i-1,j-1,k-1] = -((i-j)**2%3)*((i-k)**2%3)*((j-k)**2%3)*((j-(i%3)-0.5)**2-5/4.)
return eps.astype(int)
eps = levi_civita()
print eps
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