Optimization in R similar to MS Excel Solver
On 11-03-2013, at 23:31, Pavel_K <kuk064 at vsb.cz> wrote:
Dear all,
I am trying to find the solution for the optimization problem focused on the
finding minimum cost.
I used the solution proposed by excel solver, but there is a restriction in
the number of variables.
My data consists of 300 rows represent cities and 6 columns represent the
centres. It constitutes a cost matrix, where the cost are distances between
each city and each of six centres.
..+ 1 column contains variables, represents number of firms.
I want to calculate the minimum cost between cities and centres. Each city
can belong only to one of the centres.
A model example:
costs: distance between municipalities and centres + plus number of firms in
each municipality
"Municipality" "Centre1" "Centre2" "Centre3" "Centre4" "Centre5" "Centre6"
"Firms"
"Muni1" 30 20 60 40
66 90 15
"Muni2" 20 30 60 40
66 90 10
"Muni3" 25 31 60 40
66 90 5
"Muni4" 27 26 60 40
66 90 30
The outcome of excel functon Solver is:
cost assigned
"Municipality" "Centre1" "Centre2" "Centre3" "Centre4" "Centre5" "Centre6"
"Solution"
"Muni1" 0 20 0 0
0 0 300
"Muni2" 20 0 0 0
0 0 200
"Muni3" 25 0 0 0
0 0 125
"Muni4" 0 26 0 0
0 0 780
objective : 1405
I used package "lpSolve" but there is a problem with variables "firms":
s <- as.matrix(read.table("C:/R/OPTIMALIZATION/DATA.TXT", dec = ",",
sep=";",header=TRUE))
[2] [3] [4] [5] [6]
[1] 30 20 60 40 66 90
[2] 20 30 60 40 66 90
[3] 25 31 60 40 66 90
[4] 27 26 60 40 66 90
row.signs <- rep ("=", 4)
row.rhs <- c(15,10,5,30)
col.signs <- rep ("=", 6)
col.rhs <- c(1,1,1,1,1,1)
lp.transport (costs, "min", row.signs, row.rhs, col.signs, col.rhs,
presolve=0, compute.sens=0)
lp.transport (costs, "min", row.signs, row.rhs, col.signs, col.rhs,
presolve=0, compute.sens=0)$solution
Outcome:
Error in lp.transport(costs, "min", row.signs, row.rhs, col.signs, col.rhs,
:
Error: We have 6 signs, but 7 columns
Does anyone know where could the problem ?
Does there exist any other possibility how to perform that analysis in R ?
I am bit confused here about how can I treat with the variables "firms".
Please provide a reproducible example including the necessary library() statements. In the call of lp.transport you are using a variable "costs" but where is it defined? You read a file with read.table into a variable "s". Use dput. Berend