Stitch it is! Thanks Bill. *P bill lam wrote: > Is the ,. (stitch) what you are looking for? > pauliX (+/ .*) qb1,. qb1,. qb0,. qb0 > 1 1 0 0 > 0 0 1 1 > > I think that the mathematical definition of dot product already > suggests the right argument is operated in a column-wise manner. > > Pascal Heus wrote: >> Hi: >> I'm new to J and am trying to apply a unitary transformation to a >> collection of column vectors in a single operation. This would probably >> take a second to the J gurus out there.... >> >> Something like: >> | 0 1 | |1| |0| |0| |1| >> | 1 0 | dot |0| |1| |1| |0| >> where "dot" is the matrix product >> >> For example, I have defined a 2x2 matrix: >> pauliX =: 2 2 $ (0 1 1 0) >> >> a couple of column vectors >> qb0 =: 2 1 $ 1 0 >> qb1 =: 2 1 $ 0 1 >> >> and the matrix product >> dot =: 4 : ' x +/ . * y' >> >> and would like to write something like >> pauliX dot qb1 qb1 qb0 qb0 >> >> which should then return four column vectors with their value inverted >> (or a 2x4 matrix). >> >> Should I define a 2xN matrix first? How can I then apply the dot product >> a 2x2 matrix to each column of a 2xN matrix? >> >> Any help/suggestion would be appreciated. >> >> thanks >> Pascal >> > >
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