Oh, yes... I was just thinking of the 1j1.11e_16 case... Here's one that extends the same approach to matrices and other collections:
rd=: (+ - ]) 1j1 * >./@,@:| Thanks, -- Raul On Wed, May 2, 2012 at 10:40 AM, Bo Jacoby <bojac...@yahoo.dk> wrote: > Thank you! But it doesn't work: > rd=: (+ - ]) 1j1 * | > rd u > 1 _2.78e_17j_1.11e_16 1.11e_16j_2.22e_16 > _2.78e_17j1.11e_16 1 _2.78e_17j_1.11e_16 > 1.11e_16j2.22e_16 _2.78e_17j1.11e_16 1 > > > > > >>________________________________ >> Fra: Raul Miller <rauldmil...@gmail.com> >>Til: Programming forum <programming@jsoftware.com> >>Sendt: 14:29 onsdag den 2. maj 2012 >>Emne: Re: [Jprogramming] rounding complex numbers >> >>Here's a more general approach: >> >> rd=: (+ - ]) 1j1 * | >> >>-- >>Raul >> >>On Wed, May 2, 2012 at 6:11 AM, Bo Jacoby <bojac...@yahoo.dk> wrote: >>> Hello J'ers >>> >>> Even if a complex number is actually real it may display nonzero imaginary >>> part because of round-off errors. Adding and subtracting 1e6j1e6 removes >>> the round-off error, but is there a better or more general solution? >>> >>> UM=.%:%~_1^]%~[:+:[:*/~i. NB. Unitary Matrix generator >>> >>> rd=.]&.(1e6j1e6&+) NB. round-off cleaner >>> >>> u=.n+/ .*+n=.UM 3 NB. unit matrix >>> >>> u NB. ugly display >>> 1 _2.78e_17j_1.11e_16 1.11e_16j_2.22e_16 >>> _2.78e_17j1.11e_16 1 _2.78e_17j_1.11e_16 >>> 1.11e_16j2.22e_16 _2.78e_17j1.11e_16 1 >>> >>> rd u NB. nice display >>> 1 0 0 >>> 0 1 0 >>> 0 0 1 >>> ---------------------------------------------------------------------- >>> 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 ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
