On Tue, Jun 30, 2009 at 5:11 AM, Nils Wagner <[email protected]>wrote:
> On Tue, 30 Jun 2009 11:22:34 +0200 > "Nils Wagner" <[email protected]> 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 ? > Write it out explicitly. It essentially antisymmetrizes q and the three off diagonal elements can then be treated as a vector. Depending on how q is formed and the resulting vector is used there may be other things you can do when you use it in a more general expression. If this is part of a general calculation there might be other ways of expressing it. Chuck
_______________________________________________ Numpy-discussion mailing list [email protected] http://mail.scipy.org/mailman/listinfo/numpy-discussion
