> Sorry for the confusion, I was also confused by the description of the problem (as is implied in my first post to this thread).
:) On Wed, Aug 15, 2018 at 6:12 AM, 'Mike Day' via Programming < programm...@jsoftware.com> wrote: > Yes, I think it was ok to generalise, but I’d missed what they meant by > proportionality. > So, if I define a different quadruplet, > q=: 6 + 7*1 2 5 10 > where 1:2 = 5:10, Jose’s function works fine: > (-/ .* % -/ .+)@:(2 2&$) q > 6 > which is the required offset. > > fwiw, > dgcd q. NB. gcd of differences > 7 > (|~ dgcd) q > 6 6 6 6 > > Sorry for the confusion, > Mike > > Please reply to mike_liz....@tiscali.co.uk. > Sent from my iPad > > > On 15 Aug 2018, at 00:33, Jose Mario Quintana < > jose.mario.quint...@gmail.com> wrote: > > > > After I saw your message I searched for the particular Quora problem and > > this is what I found, > > > > https://www.quora.com/What-number-must-be-subtracted- > from-21-38-55-and-106-each-so-that-the-remainders- > technically-differences-are-proportional > > > > It seems to me that the shape of the array is restricted to be exactly 4 > > and the numbers do not have to be integers. Am I wrong? > > > > > > On Tue, Aug 14, 2018 at 7:00 PM, 'Mike Day' via Programming < > > programm...@jsoftware.com> wrote: > > > >> It should work on arrays of the form > >> a + b * i, where a and b are integer scalars, and i is an integer > >> vector. > >> So, if > >> q=: 6 + 7*1 2 5 11 23, > >> applying this function yields > >> (-/ .* % -/ .+)@:(2 2&$) q > >> 7.4 > >> I think you need instead something like > >> Difference’s greatest common divisor, > >> dgcd =: +./@:(2 -~/\ ]) > >> So > >> dgcd q > >> 7 > >> > >> It’s a bit more complicated to recover the factors, 1 2 5 ..., which > seem > >> to be required in the Quora problem: > >> (](([-|~)%])dgcd) q > >> 1 2 5 11 23 > >> This works for the original array, too, > >> (](([-|~)%])dgcd) 21 38 55 106 > >> 1 2 3 6 > >> > >> And > >> dgcd 21 38 55 106 > >> 17 > >> > >> Sorry for any formatting problems - typing on iPad, > >> > >> Mike > >> > >> > >> Please reply to mike_liz....@tiscali.co.uk. > >> Sent from my iPad > >> > >>> On 14 Aug 2018, at 23:18, Jose Mario Quintana < > >> jose.mario.quint...@gmail.com> wrote: > >>> > >>> (-/ .* % -/ .+)@:(2 2&$)21 38 55 106 > >> ---------------------------------------------------------------------- > >> 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
