Nice work, especially persuading 13 : to return a tacit version. I had reached the same solution as Pascal Jasmin’s, so not worth a comment in itself.
However, it is just about worth pointing out that the filtering approach gets expensive for larger values of y; eg 3 Smps 20 would entail filtering 2^20 rows to obtain 1140. In that case, I reckon it’s better to use the 1s indices provided by, eg, 3 comb 20 . comb is in addons/stats/base/combinatorial . In case it matters! Mike Sent from my iPad > On 31 Jul 2021, at 20:48, Raul Miller <rauldmil...@gmail.com> wrote: > > That's a bit tricky in this case, but it can be done: > > First off, the problem: > > 13 : '(#~x=+/"1)f y' NB. select row > 4 : '(#~x=+/"1)f y' > > But we can work around this by giving 13 : a variant expression: > > 13 : 't#~x=+/"1 t=.f y' > [ (] #~ [ = [: +/"1 ]) [: f ] > > And, in this example, we can turn this into a hook through inspection: > Smps=: (] #~ [ = [: +/"1 ]) f > > This could be simplified further, of course: > 2 ((] #~ (= +/"1)) f) 6 > and > 2 (((= +/"1) # ]) f) 6 > > do the same computation. > > I hope this helps, > > -- > Raul > >> On Sat, Jul 31, 2021 at 12:43 PM Srdjan Stipic <srdjan.sti...@gmail.com> >> wrote: >> >> You can use “13 : ‘…’” construct to get tacit verb. >> >> On Sat 31. Jul 2021 at 18:00, 'Pascal Jasmin' via Programming < >> programm...@jsoftware.com> wrote: >> >>> 2 ([ (] #~ [ = +/"1@:]) f@]) 6 >>> >>> >>> >>> >>> >>> >>> On Saturday, July 31, 2021, 11:52:10 a.m. EDT, 'Bo Jacoby' via Programming >>> <programm...@jsoftware.com> wrote: >>> >>> >>> >>> >>> >>> Consider this code >>> >>> f=.#&2#:[:i.2&^ NB. 0-1 rows >>> >>> >>> >>> >>> Smps=. 4 : '(#~x=+/"1)f y' NB. select rows >>> >>> 2 Smps 6 NB. for example >>> 0 0 0 0 1 1 >>> >>> 0 0 0 1 0 1 >>> >>> 0 0 0 1 1 0 >>> >>> 0 0 1 0 0 1 >>> >>> 0 0 1 0 1 0 >>> >>> 0 0 1 1 0 0 >>> >>> 0 1 0 0 0 1 >>> >>> 0 1 0 0 1 0 >>> >>> 0 1 0 1 0 0 >>> >>> 0 1 1 0 0 0 >>> >>> 1 0 0 0 0 1 >>> >>> 1 0 0 0 1 0 >>> >>> 1 0 0 1 0 0 >>> >>> 1 0 1 0 0 0 >>> >>> 1 1 0 0 0 0 >>> >>> >>> >>> I want to rewrite it tacit >>> Smps=.((=+/)"1 f)#f@] >>> This works but is without the hook, so "f" is repeated. >>> How to write the hook tacitly? >>> I believe that this is easy, but I am stuck. >>> Thank you! >>> Bo. >>> >>> >>> >>> >>> ---------------------------------------------------------------------- >>> 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 ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
