As you noted, using intersection between each item works: ([ -. -.)/ 4 5$ 1 2 3 4 5 2 3 4 5 6 5 3 7 1 8 3 8 6 1 5 3 5
You would not want to use +. unless you were specifically concerned only with the presence of prime factors. Then, for example: +./&.:(*/"1) 4 5$ 1 2 3 4 5 2 3 4 5 6 5 3 7 1 8 3 8 6 1 5 2 2 2 3 5 FYI, -- Raul On Tue, Oct 23, 2018 at 10:33 AM Skip Cave <[email protected]> wrote: > > Thanks Rob, Bo, & Mike for your enlightening answers. > > So now I have a similar question on a simpler data set: > > Given: > > g=.4 5$ 1 2 3 4 5 2 3 4 5 6 5 3 7 1 8 3 8 6 1 5 > > g > > 1 2 3 4 5 > > 2 3 4 5 6 > > 5 3 7 1 8 > > 3 8 6 1 5 > > > How do I find the common integers in g across all rows (the answer is 3 5)? > > > Rob's scheme works if I box g: > > > in each/ ~. each {g > > ┌───┐ > > │3 5│ > > └───┘ > > Or even simpler: > > in each/ {g > > ┌───┐ > > │3 5│ > > └───┘ > > I'm not sure how to apply Bo's +./ scheme to g: > > +./g > > 1 1 1 1 1 > > Same for Mike's ix verb: > > ix =: ([ -. -.) > > ix g > > 1 2 3 4 5 > > 2 3 4 5 6 > > 5 3 7 1 8 > > 3 8 6 1 5 > > > Skip > > On Tue, Oct 23, 2018 at 1:31 AM Skip Cave <[email protected]> wrote: > > > Given the integers: 1998 2997 3996 4995 5994 6993 7992 8991 > > Find the common prime factors in all of these integers. > > > > Obviously we can find the prime factors of each of the integers: > > > > q: 1998 2997 3996 4995 5994 6993 7992 8991 > > > > 2 3 3 3 37 0 0 > > > > 3 3 3 3 37 0 0 > > > > 2 2 3 3 3 37 0 > > > > 3 3 3 5 37 0 0 > > > > 2 3 3 3 3 37 0 > > > > 3 3 3 7 37 0 0 > > > > 2 2 2 3 3 3 37 > > > > 3 3 3 3 3 37 0 > > > > > > What J expression will find the common factors in all 6 of these integers? > > > > (the result of the expression should be that there are two common factors > > - 3 & 37) > > > > Skip > > > > > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
