Hi, A few comments:
1. You appear to be replying to a post on the R-Help list from 2010: https://stat.ethz.ch/pipermail/r-help/2010-June/242714.html 2. Nothing that you have below appears to be directly related to R, but to LINGO: http://www.lindo.com/index.php/products/lingo-and-optimization-modeling which appears to be a commercial product based upon a Google search. 3. If you need assistance with LINGO, contact them for support. 4. To the extent R is at all relevant to your problem, they appear to have an interface to R, which is also a commercial product: http://www.lindo.com/index.php/ls-downloads?catid=82&id=106:r-lingo-resource-page You should contact them for support with the product. 5. Even if this was related to R, this appears to be a homework problem of some type and the R lists do not assist with homework. Regards, Marc Schwartz > On Nov 10, 2017, at 11:04 AM, Jan Olsen Røyland <janoroyl...@outlook.com> > wrote: > > Hei > Im struggling with this problem: > b) Another company wants to compose the optimal project portfolio based on > the following 5- > year project proposals. In the table, the cash flow for each project in each > year is shown. > Project 1 Project 2 Project 3 Project 4 Project 5 Project 6 > 1st year of the project -58 -32 -18 -31 -33 -39 > 2nd year of the project 17 17 11 4 21 30 > 3rd year of the project 26 30 13 19 20 9 > 4th year of the project 18 7 4 7 22 13 > 5th year of the project 40 6 7 17 6 13 > In this case, the company can also choose which year each project should > commence. These six > candidate projects can begin either in 2018, in 2019 or in 2020, or not at > all. > The current proposal is to undertake project 1, 2, 3 and 5, with project 3 > and 5 starting in 2018, > project 2 in 2019 and project 1 in 2020. Available funds by the end of year > 2017 will be 70 mill. > The resulting cash flow is given in the following table: > Project 1 Project 2 Project 3 Project 5 > Total cash flow > from projects > Available > funds > 2017 70 > 2018 -18 -33 -51 19 > 2019 -32 11 21 0 19 > 2020 -58 17 13 20 -8 11 > 2021 17 30 4 22 73 84 > 2022 26 7 7 6 46 130 > 2023 18 6 24 154 > 2024 40 40 194 > Formulate an optimization model in LINGO to determine which projects to > undertake, and in which > years. The goal is to maximize available funds by the end of year 2024, while > making sure that > available funds are always non-negative throughout the planning horizon. How > much can the > improve compared to the current proposal? (For simplicity, assume zero > discount rate.) > > Med Vennelig Hilsen > Jan Olsen R�yland > ______________________________________________ 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.
