readMps {linprog}

Read MPS Files

Description

This function reads MPS files - the standard format for Linear Programming problems.

Usage

   readMps( file, solve=FALSE, maximum=FALSE )

Arguments

file

a character string naming the file to read.

solve

logical. Should the problem be solved after reading it from the file (using solveLP)?

maximum

logical. Should we maximize or minimize (the default)?

Details

Equality constraints and 'greater than'-bounds are not implemented yet.

Value

readMps returns a list containing following objects:

name

the name of the Linear Programming problem.

cvec

vector c.

bvec

vector b.

Amat

matrix A.

res

if solve is TRUE, it contains the results of the solving process (an object of class solveLP).

Author(s)

Arne Henningsen

See Also

solveLP, writeMps

Examples

## example of Steinhauser, Langbehn and Peters (1992)
## Production activities
cvec <- c(1800, 600, 600)  # gross margins
names(cvec) <- c("Cows","Bulls","Pigs")

## Constraints (quasi-fix factors)
bvec <- c(40, 90, 2500)  # endowment
names(bvec) <- c("Land","Stable","Labor")

## Needs of Production activities
Amat <- rbind( c(  0.7,   0.35,   0 ),
               c(  1.5,   1,      3 ),
               c( 50,    12.5,   20 ) )

## Write to MPS file
writeMps( "steinh.mps", cvec, bvec, Amat, "Steinhauser" )

## delete all LP objects
rm( cvec, bvec, Amat )

## Read LP data from MPS file and solve it.
lp <- readMps( "steinh.mps", TRUE, TRUE )

## Print the results
lp$res

## remove the MPS file
file.remove( "steinh.mps" )