I like the monadic equality sign (self classify): |.&=&i. 4 0 0 0 1 0 0 1 0 0 1 0 0 1 0 0 0
--- Den fre 20/8/10 skrev R.E. Boss <[email protected]>: > Fra: R.E. Boss <[email protected]> > Emne: Re: [Jprogramming] Creating a matrix (some polish required) > Til: "'Programming forum'" <[email protected]> > Dato: fredag 20. august 2010 20.32 > I like > > antid=: 1 {."0~ -@(-i.) > > antid 4 > 0 0 0 1 > 0 0 1 0 > 0 1 0 0 > 1 0 0 0 > > > R.E. Boss > > > > -----Oorspronkelijk bericht----- > > Van: [email protected] > [mailto:programming- > > [email protected]] > Namens Alex Gian > > Verzonden: vrijdag 20 augustus 2010 12:41 > > Aan: Programming forum > > Onderwerp: [Jprogramming] Creating a matrix (some > polish required) > > > > The "flipped" identity matrix is quite interesting. > (Basically it's the > > identity matrix flipped or mirrored about either the > vertical or > > horizontal axis. IOW, for a 3x3: > > 0 0 1 > > 0 1 0 > > 1 0 0 > > I don't know if it has any special name, I stumbled on > it by chance > > while messing around with a simple FSA for a puzzle > game. > > Pre-multiplying by this matrix flips any same size > matrix vertically, > > post-multiplying flips it horizontally. Its > square is obviously the > > identity matrix. > > > > Now, I have created this matrix on various systems, > (e.g. HP/RPL, > > Scheme, TI-Basic), usually - if an id matrix is > provided - just by > > reversing its rows, otherwise just by starting off > with the vector, say, > > 0 0 0 1, and then rotating the "1" each time and > appending that vector > > to a string, which is eventually converted to a > matrix. > > > > I can do this using loops and explicit coding, but am > looking for any > > suggestions to make it into a J one-liner, such that: > > flipidm 4 > > 0 0 0 1 > > 0 0 1 0 > > 0 1 0 0 > > 1 0 0 0 > > > > Hope my explanation was clear enough, > > TIA > > > > > > > > > ---------------------------------------------------------------------- > > For information about J forums see http://www.jsoftware.com/forums.htm > > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
