Off topic, but for the record... As Jeff already noted,the equation reduces to a single linear equation with rational coefficients, so of course there are infinitely many integer solutions.
Apologies for my dummheit. -- Bert On Fri, Dec 8, 2017 at 9:47 AM, Bert Gunter <bgunter.4...@gmail.com> wrote: > Please keep all replies onlist if there is no reason to keep them private. > I am not a free, private consultant (and so might choose to ignore your > followups); and I don't have all or necessarily the best answers anyway. So > give yourself the maximal chance to be helped by others. > > Anyway, > > ?expand.grid is what you're looking for I think as an alternative to > nested loops. If "results" is a vector of calculated results, i.e. the > averages for the grid of combinations you generate, and "target" is your > desired target (average), here of 15.0078, then > > which.min(abs(results - target)) > gives you the index of the closest results and > > abs(results - target) < tol > gives you a vector of logicals of results that are within tol of the > target. > > This is all pretty basic stuff, which suggests that you really need to > spend some time with an R tutorial or two. Here are some suggestions, but > a web search would uncover many more, some of which might be more suitable > for you: > https://www.rstudio.com/online-learning/#R > > This list can help (not sure if I did here), but it cannot replace such > homework on your own. > > Cheers, > Bert > > > > > Bert Gunter > > "The trouble with having an open mind is that people keep coming along and > sticking things into it." > -- Opus (aka Berkeley Breathed in his "Bloom County" comic strip ) > > On Fri, Dec 8, 2017 at 9:15 AM, Benjamin Sabatini <sunsca...@hotmail.com> > wrote: > >> Hi, >> >> Yes, actually, I could set an upper limit and grind through the >> possibilities to find a minimal set or a few if that's what you mean. Close >> to the result would be OK, too. Otherwise it would go on forever, I >> suppose. >> >> At first I was thinking of just trying to write three for loops to test >> for every set of the multiples of x, y, and z between something like 1 and >> 10,000, but I understand that this is not at all efficient in R. So, >> (1*13.4689 >> + 1*12.85212+ 1*17.05071) / 1+1+1), (1*13.4689 + 2*12.85212+ 1*17.05071) >> / 1+2+1)... >> >> Is there a better way? If I solve for z is it then easier with an upper >> limit? So, z = x*0.753288 + y*1.0552 >> and then loop it? >> >> ------------------------------ >> *From:* Bert Gunter <bgunter.4...@gmail.com> >> *Sent:* Friday, December 8, 2017 3:16 PM >> *To:* Jeff Newmiller >> *Cc:* R-help; Benjamin Sabatini >> *Subject:* Re: [R] trying to find the multiple combinations... >> >> Are x,y, and z supposed to be positive whole numbers? If so, there may be >> no solutions. If there is a solution set, of course any multiple of the set >> is a solution set, so presumably you want a minimal set in some sense. This >> strikes me as a hard problem mathematically, but maybe there is some >> obvious way to set an upper bound on a minimal x,y, and z, in which case a >> simple grid search could then be used. >> >> Naturally, if any real numbers are sought, Jeff is correct. >> >> Cheers, >> Bert >> >> >> >> Bert Gunter >> >> "The trouble with having an open mind is that people keep coming along >> and sticking things into it." >> -- Opus (aka Berkeley Breathed in his "Bloom County" comic strip ) >> >> On Fri, Dec 8, 2017 at 12:19 AM, Jeff Newmiller <jdnew...@dcn.davis.ca.us >> > wrote: >> >> Solve for one of your variables and it will be given in terms of the >> other two. That is, there is a whole infinite plane of solutions. No, >> aggregate will not be sufficient to enumerate the solution set.. >> -- >> Sent from my phone. Please excuse my brevity. >> >> On December 7, 2017 10:37:37 PM PST, Benjamin Sabatini < >> sunsca...@hotmail.com> wrote: >> >Hi, >> > >> >I'm trying to find a way to determine what multiples of the combination >> >of three or more numbers equals a forth number. >> > >> >So, if I had a number set like: >> > >> >c(13.4689, 12.85212, 17.05071) >> > >> >What combination and multiples of these numbers would average to >> >15.0078? (so, something that would tell me x, y, and z in (x*13.4689 + >> >y*12.85212+ z*17.05071) / x+y+z) = 15.0078 >> > >> >I think this is doable with aggregate? >> > >> > [[alternative HTML version deleted]] >> >> This is a plain text mailing list. Please learn how to use your email >> program. >> >> > >> >______________________________________________ >> >R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see >> >https://stat.ethz.ch/mailman/listinfo/r-help >> >PLEASE do read the posting guide >> >http://www.R-project.org/posting-guide.html >> >and provide commented, minimal, self-contained, reproducible code. >> >> ______________________________________________ >> R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see >> https://stat.ethz.ch/mailman/listinfo/r-help >> PLEASE do read the posting guide http://www.R-project.org/posti >> ng-guide.html >> and provide commented, minimal, self-contained, reproducible code. >> >> >> > [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
