8
votes
Reducing number of suppliers for product portfolio
You can model this as a set covering problem (or hitting set problem -- different terminology, same mathematical model). The (binary) decision variables would determine which suppliers you select; the ...
- 40.1k
8
votes
When should I use a solver for IP and MIP and can I just use a library from Python, R, Matlab, etc...?
I assume the solver you're referring to in Python/R/Matlab, are the open-source solvers such as CBC or GLPK (you can find out more in this question: Where can I find open source LP solvers?). If that'...
- 5,894
7
votes
Using R for coding Matheuristic for Research Publication
You mention data pre-/post-processing. If what you propose to do is in the context of data science (for instance, a matheuristic for outlier identification to be embedded in some statistical data-...
- 40.1k
7
votes
Queuing models in R, $\lambda$ Little
Not directly answering your question of how to code it manually but for discrete simulation of queues in R I would strongly recommend the simmer package. The ...
- 1,343
6
votes
VRP package for R
The package netgen (v1.3) can be used to generate networks and benchmark instances of VRP and TSP.
As this article shows it is also possible to solve a variant of ...
- 5,452
5
votes
Accepted
Solving Capacitated VRP with multiple various sized vehicles
You could cluster 40,000 dropping locations (by grouping them based on location/vehicle type need) to some reasonable number and can try to implement metaheuristics like Simulated annealing, Particle ...
- 994
5
votes
Accepted
Is it possible to merge two objective functions using the LpSolve package in R?
There are a variety of ways to deal with multiple objectives, so the answer is "it depends".
Probably the most common approach is to optimize a weighted sum or difference of the individual ...
- 40.1k
5
votes
Optimization gives me negative value
The ompr::add_variable function has a default value of -Inf for the lower bound (lb) ...
- 40.1k
4
votes
3D Knapsack Problem: R or Python Packages?
As the container loading problem is NP-hard in its essence, therefore, using a mixed-integer program might not be efficient to solve this kind of problem, except using advanced techniques like column ...
- 9,248
4
votes
Linear Programming problem for finding supplier
The problem you mentioned sounds like a variant of the lot-sizing problem in which there are multiple sources to produce one of the materials. Let's say, the variable $x_{i,s,t}$ represents the amount ...
- 9,248
4
votes
Accepted
Optimizing a capacitated clustering problem with Greedy search algorithm
Your distance constraint for each cluster limits the sum of the distance from each cluster point to its nearest neighbor (excluding the last point selected for the cluster, whose nearest neighbor is ...
- 40.1k
4
votes
Solving Capacitated VRP with multiple various sized vehicles
I'm not an expert in Vehicle Routing Problems, maybe someone else will have something more relevant to propose.
I think that a good starting point is this article:
"Efficiently solving very large-...
- 2,673
4
votes
VRP package for R
I guess it is a bit late now, but recently I have been developing a package for solving large instances of the capacitated multiple-depot vehicle routing problem with mileage constraints, which is ...
4
votes
When should I use a solver for IP and MIP and can I just use a library from Python, R, Matlab, etc...?
The main reasons are performance and quality of numerics. Non-professional stuff tend to lack the polish professionals spend time doing to ensure that numerical issues don't compromise the solving ...
- 12.2k
4
votes
Adjust result to equal mode values
You are looking for a transversal or system of distinct representatives. One approach is to construct a bipartite graph with a left node for each alternative $i$, a right node for each mode $j$, and ...
- 33.6k
4
votes
Accepted
Assign jobs to least people with multiple job constraints
Let $I$ be the set of available persons (you can set this value to an upper bound, e.g. 6 in your case),and $J$ be the set of jobs. $S$ is the set of shifts. $R_j$ is the amount of hours a job needs ...
- 1,726
3
votes
Reducing number of suppliers for product portfolio
Let $b_{i,j}$ denote product $i$ is taken from supplier $j$. and $x_j$ denote whether supplier $j$ is selected once or not.
$i \in n$ (product) $j \in m$ (supplier)
Now:
\begin{align}\max&\quad \...
- 1,589
3
votes
Accepted
DAG shortest path in R - I have a list of nodes, each node's completion time and each node's predecessor(s). How can I turn this to a list of arcs?
The problem here seems to be that the data is provided in a somewhat untidy fashion. To use the function the data needs to be preprocessed to extract each entry from the column "Predecessor(s)". You ...
- 2,767
3
votes
Problems with reading CPLEX LP models from file in R by package 'lpSolveAPI'
The first issue is that "LP" format means different things to lpsolve and CPLEX. See the warning about that near the top of the lpsolve page describing their format. There are converters ...
- 40.1k
3
votes
Solving Capacitated VRP with multiple various sized vehicles
I'm assuming in what follows that all demands must be met.
R has a very good genetic algorithm package ("GA") that includes support for permutation chromosomes. Assuming $n$ destinations and ...
- 40.1k
3
votes
Accepted
How to Use the Weighted Sum Method in R
The GeeksForGeeks page linked in your previous question provides one possible way to scale your attributes. Using that scaling method, your code is correct and two clusters has the highest performance ...
- 40.1k
3
votes
Accepted
Use the Weighted Sum Method in R
The edited version fixed one problem (numeric fields being character strings). Before using the weightedSum function (or doing any other calculations), you also ...
- 40.1k
3
votes
Accepted
Using R for coding Matheuristic for Research Publication
A couple of years ago we had a student who wanted to call CPLEX from R and I think after spending a lot of time with a colleague they couldn't get it to work. The situation may have been improved, but ...
- 2,110
3
votes
Accepted
Adjust result to equal mode values
There is no guarantee you can avoid ties using mode (or anything else, if it is possible for two alternatives to have identical scores and thus be indistinguishable). Rob's approach (which I endorse) ...
- 40.1k
3
votes
Include dataframe linear optimization in r
MILP modelling in R is not as advanced or convenient as it is in Python or Julia. Few exceptions I know about are ROI and ompr packages. ompr seems to be actively maintained thanks to Dirk Schumacher.
...
- 361
3
votes
Accepted
Two criteria in a problem that involves multiple-criteria decision-making
More criteria would not necessarily help, and in fact might make it harder to make a selection (for instance, if every alternative excels on some criterion and does badly on some other criterion). ...
- 40.1k
3
votes
Grouping values based on a difference constraint
Some of this may be solver dependent. I just ran your model with only one change -- switching the solver from glpk to CPLEX -- and got a valid solution (the same as yours, changing group 10 to group 2)...
- 40.1k
3
votes
Grouping values based on a difference constraint
Since you've a threshold (diff) you may pre-define max of diff number of groups, not the full length of the list.
As for the if condition try this
$L(x_{i,g}+x_{j,g}-1) \le d - (L_j - L_i)$
where $L$ ...
- 3,513
3
votes
Accepted
How to Group IDs Based on the Difference of Each ID’s Min and Max Value?
Sounds like shift scheduling, where each id is a shift with start time equal to the min value and end time equal to the max value. Your first condition requires at least a certain amount of rest ...
- 33.6k
2
votes
Linear Programming problem for finding supplier
As @prubin corretly pointed out, the essential problem at hand is the transportation problem with some additional constraints on non-available quantities for relevant material-supplier pairs.
I could ...
- 183
Only top scored, non community-wiki answers of a minimum length are eligible