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#######################################################################
# TSP - Traveling Salesperson Problem
# Copyrigth (C) 2011 Michael Hahsler and Kurt Hornik
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
## create a TSP problem
TSP <- function(x, labels = NULL) {
if(inherits(x, "TSP")) return(x)
x <- as.TSP(x)
if(!is.null(labels)) attr(x, "Labels") <- labels
x
}
## coercion
as.TSP <- function(x) UseMethod("as.TSP")
as.TSP.dist <- function(x){
## make sure we have a upper triangle matrix w/o diagonal
x <- as.dist(x, diag = FALSE, upper = FALSE)
## make sure we have labels
if(is.null(attr(x, "Labels"))) attr(x, "Labels") <- c(1:n_of_cities(x))
if(any(is.nan(x))) stop(paste(sQuote("NAs"), "not supported"))
## make sure data is numeric
mode(x) <- "numeric"
class(x) <- c("TSP", class(x))
x
}
as.TSP.matrix <- function(x){
if(!isSymmetric(x)) stop("TSP requires a symmetric matrix")
method <- attr(x, "method")
x <- as.dist(x, diag = FALSE, upper = FALSE)
attr(x, "method") <- method
## make sure we have labels
if(is.null(attr(x, "Labels")))
attr(x, "Labels") <- c(1:n_of_cities(x))
if(any(is.nan(x))) stop(paste(sQuote("NAs"), "not supported"))
## make sure data is numeric
mode(x) <- "numeric"
class(x) <- c("TSP", class(x))
x
}
as.dist.TSP <- function(m, ...) {
class(m) <- "dist"
m
}
## print
print.TSP <- function(x, ...) {
method <- attr(x, "method")
if(is.null(method)) method <- "unknown"
cat("object of class", sQuote(class(x)[1]), "\n")
cat(n_of_cities(x), "cities",
paste("(distance ", sQuote(method),")", sep=""), "\n")
}
## number of cities
n_of_cities.TSP <- function(x) attr(x, "Size")
## generic for n_of_cities
n_of_cities <- function(x) UseMethod("n_of_cities")
n_of_cities.default <- n_of_cities.TSP
## labels
labels.TSP <- function(object, ...) attr(object, "Labels")
## image
image.TSP <- function(x, order, col = gray.colors(64), ...) {
p <- n_of_cities(x)
if(missing(order)) order <- 1:p
graphics::image.default(1:p, 1:p, as.matrix(x)[order, order],
col = col, ...)
}
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