Also, here is a generic verb which makes a sparse from indices and values (isn't there a better way ?)
sp=: ]`(<"[EMAIL PROTECTED])`(1: $. 1: + >./@[) } (,.~&i. ; 1:) 5 +---+-+ |0 0|1| |1 1| | |2 2| | |3 3| | |4 4| | +---+-+ (,.~&i. sp 1:) 5 0 0 | 1 1 1 | 1 2 2 | 1 3 3 | 1 4 4 | 1 --- "R.E. Boss" <[EMAIL PROTECTED]> wrote: > Sparse is not used yet: > I34=: 1: ([`(] ;/@,[EMAIL PROTECTED]@#)`])} 1:$.,~ > > > > -----Oorspronkelijk bericht----- > Van: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Namens Roger Hui > Verzonden: donderdag 23 maart 2006 17:59 > Aan: Programming forum > Onderwerp: Re: [Jprogramming] monad e. > > Efficiency is usually not the main concern when generating > the identity matrix. You'd run out of space well before > the time would matter. > > I myself prefer the really short methods, for example, [EMAIL PROTECTED] > > > > ----- Original Message ----- > From: "R.E. Boss" <[EMAIL PROTECTED]> > To: "'Programming forum'" <[email protected]> > Sent: Thursday, March 23, 2006 8:23 AM > Subject: RE: [Jprogramming] monad e. > > Your method seems to be equivalent to I3a in > http://www.jsoftware.com/jwiki/Essays/Identity_Matrix but nothing is said > there about performance. > > R.E. Boss > > > > -----Oorspronkelijk bericht----- > Van: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Namens Devon McCormick > Verzonden: donderdag 23 maart 2006 17:05 > Aan: Programming forum > Onderwerp: Re: [Jprogramming] monad e. > > I use the following to produce an identity matrix because it's faster: > idMat=: 2&$ $ ([: >: ]) {. 1"_ > which is a tacit version of > idMat=: 3 : '(2$y.)$(>:y.){.1' > > Can't say I've ever used monadic e. but I like Oleg's pictures. > > On 3/22/06, Henry Rich <[EMAIL PROTECTED]> wrote: > > > > Except for e. i. n to produce an identity matrix, has anybody > > ever used monad e. ? > > > > Henry Rich > > > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
