On Thu, Nov 15, 2012 at 7:49 PM, Sam Asin <asin....@gmail.com> wrote: > Hey, > > It's actually not homework, what gave you that impression?
Real data sets don't usually have people named A,B,C with wages 3,4,5. ;-) To your question at hand, it's close to a classic problem in combinatorial optimization known as the knapsack problem, but there are some small differences. That's a difficult (in a technical sense) problem but well-studied so there are lots of good "almost solutions." I'd look into that and see if you can transform it to fit that framework, for which there is almost surely a CRAN-tested implementation available. > I graduated in > May and studied Math, economics, and international relations, so I don't > have much of a programming background. This is a project that I'm working > on out of personal interest. > > Obviously, I've tried doing some homework, but after 45 minutes of digging > around without even really having any leads I figured I would post here. > > The optimization problems I see more generally seem tailored towards > maximizing a function subject to some constraint on that function. For > example, maximizing U(x,y)=2x^2+4y s.t. x+y=3. I don't really see a way to > frame my current maximization like that at all. We aren't choosing one > observation in our dataset, we are choosing a group. And, the constraints > aren't something like the types sum to a number, but rather that our choice > of observations meet some specific condition. > > Sorry if I'm being clueless here, but when I look at > http://cran.r-project.org/web/views/Optimization.html I just see a giant > list of packages, most of which I believe are optimizing a function subject > to constraints. Maybe my problem actually is a common one, there is some > package out there that would do it, and I just need to find it. If so, my > googling and looking on the help pages has been so far unsuccessful. I > apologize if the answer really is sitting there on some help page, but I > really haven't found it. If this were some homework problem, then I would > know that it's probably a common, normal thing, and feel more confident > looking on the Cran page. But, since it isn't, I wasn't even sure if the > answer was out there and my searching had so far been fruitless. That's > why I wanted to know if there would be some function that would do this > sort of thing or if it's the sort of thing that I just need to manually > work through. > > The help pages are over my head in so far as the help pages are highly > technical and focused on methods. They assume a knowledge about the basic > type of optimization problem that I don't have, and I think that's because > there is a standard type of optimization that is most common. > > Anyways, I am thinking I might just try to manually do the calculation > because I can't follow the optimize commands. The general strategy I think > is to somehow make a dataset that has all combinations of 6 people as rows. > Then, for each row, make a vector that is just all the types of the people > in that row, a vector for the sum of the values, and a vector for the sum > of the wages. Then, keep only those rows which have the correct types and > wages under the max. Then, sort by the sum of the values. Let me know if > you have any better ideas! > > Sam > > > On Wed, Nov 14, 2012 at 7:35 PM, Bert Gunter <gunter.ber...@gene.com> wrote: > >> Sam: >> >> 1. Homework? R has a no homework policy. >> >> 2. But in any case, check out the Optimization task view on CRAN. You >> should be able to find something there that meets your needs. >> >> Of course, if something is "a little over your head," that's not an >> excuse, but rather an admission that you have to do some "homework" on >> your own. >> >> Cheers, >> Bert >> >> On Wed, Nov 14, 2012 at 5:23 PM, Sam Asin <asin....@gmail.com> wrote: >> > Hello, >> > >> > I am fairly new with R and am having trouble finding an optimal group. I >> > checked the help functions for the various optimize commands and it was a >> > little over my head. >> > >> > I have a dataset with 4 columns, name, type, value, and cost. The set >> > consists of a list of people, which have 3 types. I want to choose 6 >> > people, two of each type, and maximize the sum of their values. However, >> > I'm subject to the constraint that the wage of the three people has to >> sum >> > to less than 20 dollars. Here is some sample data. >> > >> > people <- c("A", "B", "C", "D", "E", "F", "G", "H", "I") >> > type<- c(1, 1, 1, 1, 2, 2, 3, 3, 3) >> > value<-c(25.20, 24, 38, 20, 14, 20, 31, 11, 8) >> > wage<- c(4, 3.8, 5.1, 3.5, 2.4, 3, 6, 2.4, 2) >> > >> > data<- data.frame(people, type, value, wage) >> > >> > With this small dataset the question isn't very interesting, but the >> answer >> > would be something like person C, D, E, F, G, and I (I didn't check to >> see >> > that those prices sum to less than $20). >> > >> > How can I write a program that will do this? Can I just use the optimize >> > command? Do I have to transform my dataset into something that is easier >> > to use the optimize command on? Or should I write my own code that does >> > the process? >> > >> > Thanks, >> > >> > Sam >> > >> > [[alternative HTML version deleted]] >> > >> > ______________________________________________ >> > R-help@r-project.org mailing list >> > 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. >> >> >> >> -- >> >> Bert Gunter >> Genentech Nonclinical Biostatistics >> >> Internal Contact Info: >> Phone: 467-7374 >> Website: >> >> http://pharmadevelopment.roche.com/index/pdb/pdb-functional-groups/pdb-biostatistics/pdb-ncb-home.htm >> > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@r-project.org mailing list > 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 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.
