This is not as direct as the solutions using expansion with a complex expander but it's one of those things I thought of and it worked the first time just as I'd conceived it: concatenation under rotation:
0,&.(4&|."1)0,&.(4&|.)>:i.5 5 1 2 3 4 0 5 6 7 8 9 0 10 11 12 13 14 0 15 16 17 18 19 0 20 0 0 0 0 0 0 21 22 23 24 0 25 The only advantage it might have would be for inserting non-zero rows or columns. The symmetry of inserting both the same row and column makes me wonder if there's a more general, adverbial method to do both at once. Experimentation showed me this: (0&,&.(4&|.)) (1 : 'u u"1 y')mat 1 2 3 4 0 5 6 7 8 9 0 10 11 12 13 14 0 15 16 17 18 19 0 20 0 0 0 0 0 0 21 22 23 24 0 25 Which extends interestingly (though maybe not usefully): (0 99&,&.(4&|.)) (1 : 'u u"1 y')mat 1 2 3 4 0 99 5 6 7 8 9 0 99 10 11 12 13 14 0 99 15 16 17 18 19 0 99 20 0 99 0 0 0 0 0 21 22 23 24 0 99 25 On Fri, Jan 9, 2009 at 4:47 PM, Raul Miller <[email protected]> wrote: > On Fri, Jan 9, 2009 at 4:40 PM, Brian Schott <[email protected]> > wrote: > > I think this is more complete. > > > > 1 1 1 1j1 1 #"1]1 1 1 1j1 1 #>:i. 5 5 > > 1 2 3 4 0 5 > > 6 7 8 9 0 10 > > 11 12 13 14 0 15 > > 16 17 18 19 0 20 > > 0 0 0 0 0 0 > > 21 22 23 24 0 25 > > Yes, thank you, I did not read carefully enough. > > Or: > m=:1+i.5 5 > b=:1 1 1 1 0 1 > b #inv b#inv"1 m > 1 2 3 4 0 5 > 6 7 8 9 0 10 > 11 12 13 14 0 15 > 16 17 18 19 0 20 > 0 0 0 0 0 0 > 21 22 23 24 0 25 > > -- > Raul > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > -- Devon McCormick, CFA ^me^ at acm. org is my preferred e-mail ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
