TSP (version 1.1-4)

TSPLIB: Read and write TSPLIB files

Description

Reads and writes TSPLIB format files. TSPLIB files can be used by most TSP solvers. Sample instances for the TSP in TSPLIB format are available on the TSPLIB homepage (see references).

Usage

write_TSPLIB(x, file, precision = 6, inf = NULL, neg_inf = NULL)
read_TSPLIB(file, precision = 0)

Arguments

x

an object of class TSP, ATSP or ETSP. NAs are not allowed.

file

file name or a connection.

precision

controls the number of decimal places used to represent distances (see details). If x already is integer, this argument is ignored and x is used as is.

inf

replacement value for Inf (TSPLIB format cannot handle Inf). If inf is NULL, a large value of $max(x) + 2 range(x)$ (ignoring infinite entries) is used.

neg_inf

replacement value for -Inf. If no value is specified, a small value of $min(x) - 2 range(x)$ (ignoring infinite entries) is used.

Value

read_TSPLIB returns an object of class TSP or ATSP.

Details

In the TSPLIB format distances are represented by integer values. Therefore, if x contains double values (which is normal in R) the values given in x are multiplied by $10^{precision}$ before coercion to integer. Note that therefore all results produced by programs using the TSPLIB file as input need to be divided by $10^{precision}$ (i.e., the decimal point has to be shifted precision placed to the left).

Currently only the following EDGE_WEIGHT_TYPEs are implemented: EXPLICIT, EUC_2D and EUC_3D.

References

TSPLIB home page, http://www.iwr.uni-heidelberg.de/groups/comopt/software/TSPLIB95/

Examples

## Drilling problem from TSP
drill <- read_TSPLIB(system.file("examples/d493.tsp", package = "TSP"))
drill
tour <- solve_TSP(drill, method = "nn", two_opt = TRUE)
tour
plot(drill, tour, cex=.6, col = "red", pch= 3, main = "TSPLIB: d493")

  
## Write and read data in TSPLIB format
x <- data.frame(x=runif(5), y=runif(5))

## create TSP, ATSP and ETSP (2D)
tsp <- TSP(dist(x))
atsp <- ATSP(dist(x))
etsp <- ETSP(x[,1:2])  
  
write_TSPLIB(tsp, file="example.tsp")
#file.show("example.tsp")
r <- read_TSPLIB("example.tsp")  
r  
  
write_TSPLIB(atsp, file="example.tsp")
#file.show("example.tsp")
r <- read_TSPLIB("example.tsp")  
r  
  
write_TSPLIB(etsp, file="example.tsp")
#file.show("example.tsp")
r <- read_TSPLIB("example.tsp")  
r  
  
## clean up
unlink("example.tsp")