Rglpk_read_file function

Interface to GLPK's file reader

High level R interface to the CPLEX_LP, MATHPROG and MPS reader of the GNU Linear Programming Kit (GLPK). Example data from the GLPK release is included in the './examples/' sub-directory.

## File reader for various formats
Rglpk_read_file(file, type = c("MPS_fixed", "MPS_free", "CPLEX_LP", "MathProg"),
ignore_first_row = FALSE, verbose = FALSE) 

## print method
## S3 method for class 'MP_data_from_file'
print(x, ...)

Arguments

• file: a character string specifying the relative or absolute path to the model file.
• type: a character string specifying the file format. This can be either "MPS_fixed", "MPS_free", "CPLEX_LP", and GNU "MathProg".
• ignore_first_row: a logical indicating whether the first row of the model file should be ignored or not. Default: FALSE.
• verbose: a logical for turning on/off additional solver output. Default: FALSE.
• x: an object of class "MP_data_from_file".
• ``: further arguments passed on to the print method.

Details

Rglpk_read_file() takes the path to a file as an argument and calls GLPK's file reader. The description of the linear or mixed integer linear program is returned as an object of class "MP_data_from_file".

Returns

Rglpk_read_file() returns the specification of a (mixed integer) linear program defined in file as an object of class "MP_data_from_file". The returned object is a list containing the following components.

• objective: a "simple_triplet_matrix" representing the coefficients to $x$ in the objective function.

• constraints: a list with three elements: a "simple_triplet_matrix" of coefficients, a character vector of constraint directions, and a numeric vector representing the right hand side.

• bounds: a list containing two elements: lower and upper. Each of which contain a list specifying indices (ind) and corresponding bounds (val).

• types: a character vector specifying whether the corresponding objective variable is of type binary ("B"), continuous ("C"), or integer ("I").

• maximum: a logical indicating whether a minimum or a maximum is sought.

Further meta data is provided as attributes to the object.

Author(s)

Stefan Theussl

Examples

## read a CPLEX LP file
x <- Rglpk_read_file( system.file(file.path("examples", "plan.lp"), package
= "Rglpk"), type = "CPLEX_LP")
x
## optimal solution: 296.2166
Rglpk_solve_LP(x$objective, x$constraints[[1]], x$constraints[[2]],
                x$constraints[[3]], x$bounds, x$types, x$maximum)
## read a MATHPROG file
x <- Rglpk_read_file( system.file(file.path("examples", "assign.mod"), package
= "Rglpk"), type = "MathProg")
x
## optimal solution: 76
Rglpk_solve_LP(x$objective, x$constraints[[1]], x$constraints[[2]],
                x$constraints[[3]], x$bounds, x$types, x$maximum)
## read a MATHPROG file
x <- Rglpk_read_file( system.file(file.path("examples", "plan.mps"), package
= "Rglpk"), type = "MPS_fixed")
x
## optimal solution: 296.2166
Rglpk_solve_LP(x$objective, x$constraints[[1]], x$constraints[[2]],
                x$constraints[[3]], x$bounds, x$types, x$maximum)