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Questions tagged [ompr]

25 questions
3
votes
1 answer

In the ompr package in R, how can I rephrase my objective/constraints/variables so as to avoid the "problem too large" error?

I am trying to learn to fit a linear integer programming optimization model in R using the ompr package that a colleague had previously fit using CPLEX/GAMS (specifically, the one described here: Haight et al. 2021). I am running my implementation…
Bajcz
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4 answers

Is there a way to define a complex objective function in an R optimizer?

In R, I am trying to optimize the following : choose rows which maximize the number of columns whose sum exceeds a certain value which varies by column + some other basic constraints on the row selections. Is there anything out there in R which…
Benjamin Battle
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3 answers

MIP (ompr) model taking too much time to solve in R

I am trying to solve a capacitated facility location problem in R. The sample data for that: n<- 500 #number of customers m<- 20 #number of facility centers set.seed(1234) fixedcost <- round(runif(m, min=5000, max=10000)) warehouse_locations <-…
Shibaprasadb
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Optimisation in R: Creating an exam schedule (ompr, ROI ?)

I'm scheduling an exam for a course (using R). I have 36 students, which all need to be fitted with time-slots to 8 teachers on the exam day (1:1 exams). Each student or teacher can obviously only be in one place at a time. How do I run an…
Silviculturalist
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ompr.highs package not working on my computer

Since i have changed my computer i have an issue with the ompr.highs package. I ran this exemple code : library(ompr) library(ompr.highs) suppressPackageStartupMessages(library(dplyr, quietly = TRUE)) max_bins <- 10 bin_size <- 3 n <- 10 weights <-…
Mousta1101
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1 answer

Need help to add a constraint to a MIP model in R

I'm trying to build a model to optimize steel production. The objective is to reduce the amount of waste (leftover material after the steel has been cut). The code below is what I have so far. It is lacking a constraint to make sure that each item…
RegressionSquirrel
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2 answers

Transportation cost optimisation using OMPR for a large data set

I am solving a transport optimization problem given a set of constraints. The following are the three key data sets that I have #demand file demand - has demand(DEMAND) across 4821(DPP) sale points(D) head(demand) D PP…
Srikanth Viswanathan
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How to solve "index not found error" in ompr package R?

I'm using ompr package to develop BIN PACKING problem as staed in the following link: https://developers.google.com/optimization/bin/bin_packing This is the code I run: # Import lpSolve package library(lpSolve) #Import required…
Diego Fabbri
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0 answers

R OMPR- Adding a new constraint and dimension to matrix

I'm using the OMPR package in r in order to solve some constraint problems with my keeper-league soccer/football team. This league is operated very much like a real Premier League team, where I wanted to maximize the total number of goals…
BigDawgBigBite
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How to define 3D variable in OMPR package of R?

I am trying to solve a MILP supply network optimization problem using R's OMPR package. I need to define a 3D binary variable (x[i,j,q]) in the model to map Customers (i) to DC (j) by each SKU (q). Does anyone know how I can do that? With my current…
Samidha
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1 answer

ompr MILPModel : non-numeric argument to binary operator

I am familiar with how to use ompr::MIPModel but am trying to learn how to use MILPModel to take advantage of the model build speed. A simplified version of my model is below. I have two decision variables, x and y, binary and of equal length. I…
Ralph Asher
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1 answer

R: ompr package constraints

I am using ompr package in R to solve an omptimization problem. The optimization problem in written looks like this: Min wi * xi xi ϵ {0,1} xi ≤ xj , j follower of i i is a follower of j if in the distance matrix (distmatrix) a value is available.…
Mara
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optimize function to maximimize value given a list of unique numbers

I have a function that calculates the total value given a vector of unique integer numbers. For example, in the problem below i would like to find the maximum value by changing the vector numbers. Constraints are that the vector must be a length of…
jsimpsno
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1 answer

Optimization - big M approach ompr

I'm trying to implement the big M approach to a simple problem but I'm struggling a lot as I'm new on optimization tasks. I'm using the ompr package to solve the folowing problem: Trying to minimise the sum of puchase cost defined as: sum("needed"…
jimprideaux
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1 answer

How to force minimum number of groups in linear programming problem using ompr

The following problem seeks to maximize the weight across any 3 items while being under a cost of 20. I gave group "a" a large weight so that the model will only select the 3 items from group "a". How do I force the model to include at least 2…
Giovanni Colitti
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