Package 'tabuSearch'

R Based Tabu Search Plot Function

Description

Plots features of an optimization run of the tabu search algorithm for binary strings. The default plots show: (a) the number of times each element of the string was set to one over the search, (b) frequency of moves for each element of the string over the serach, (c) the number of ones in the chosen configuration at each iteration, (d) the objective function value of the current configuration at each iteration of the algorithm. The "tracePlot" shows the current configurations for all interations.

Usage

## S3 method for class 'tabu'
plot(x, type = "default", ...)

Arguments

x	a tabu object.
type	"tracePlot" or default.
...	options directly passed to the plot function.

Examples

# A simple example

evaluateSimple <- function(th)return(1)
result <- tabuSearch(size = 20, iters = 100, objFunc = evaluateSimple) 

plot(result)
plot(result, "tracePlot")

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R Based Tabu Search Summary Function

Description

Summarizes the results of a tabu search optimization run.

Usage

## S3 method for class 'tabu'
summary(object, verbose = FALSE, ...)

Arguments

object	a tabu object.
verbose	if true, the optimal configuration(s) will be printed.
...	other options (ignored).

Examples

# A simple example

evaluateSimple <- function(th)return(1)
result <- tabuSearch(size = 20, iters = 100, objFunc = evaluateSimple) 

summary(result)
summary(result, verbose = TRUE)

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R based tabu search algorithm for binary configurations

Description

A tabu search algorithm for optimizing binary strings. It takes a user defined objective function and reports the best binary configuration found throughout the search i.e. the one with the highest objective function value. The algorithm can be used for variable selection.

The results can be plotted and summarized using plot.tabu and summary.tabu.

Usage

tabuSearch(size = 10, iters = 100, objFunc = NULL, config = NULL, 
neigh = size, listSize = 9, nRestarts = 10, repeatAll = 1, verbose = FALSE)

Arguments

size	the length of the binary configuration.
iters	the number of iterations in the preliminary search of the algorithm.
objFunc	a user supplied method that evaluates the objective function for a given binary string. The objective function is required to take as an argument a vector of zeros and ones.
config	a starting configuration.
neigh	a number of neighbour configurations to check at each iteration. The default is all, which is the length of the string. If neigh < size, the neighbours are chosen at random.
listSize	tabu list size.
nRestarts	the maximum number of restarts in the intensification stage of the algorithm.
repeatAll	the number of times to repeat the search.
verbose	if true, the name of the current stage of the algorithm is printed e.g. preliminary stage, intensification stage, diversification stage.

Value

A tabu object which is a list giving:

configKeep	a matrix of configurations chosen at each iteration of the algorithm.
eUtilityKeep	value of the objective function for the above configurations.
iters	the number of iterations in the preliminary search of the algorithm.
neigh	a number of neighbour configurations checked at each iteration.
listSize	tabu list size.
repeatAll	the number of times the search was repeated.

Author(s)

K. Domijan

References

Glover, F., 1977. Heuristics for integer programming using surrogate constraints. Decision Sciences 8, 156-166.

Glover, F., 1986. Future paths for integer programming and links to artificial intelligence. Computers and Operations Research 13, 533-549.

Fouskakis, D., Draper, D., 2002. Stochastic optimization: a review. International Statistical Review 70, 315-349.

See Also

plot.tabu summary.tabu

Examples

# A simple example


evaluateSimple <- function(th)return(1)

result <- tabuSearch(size = 20, iters = 100, objFunc = evaluateSimple) 


## Not run: 
# simulate 10-d data: 150 samples from 3 bivariate normals and 8 noise variables. 
# Variable selection should recover the first two variables




library(MASS)
NF <- 10
G <- 3
NTR <- 50
NTE <- 50

muA <- c(1,3)
SigmaA <- matrix(c(0.2, 0.04, 0.04, 0.2), 2, 2)
muB <- c(1.2,1)
SigmaB <- matrix(c(0.1, -0.06, 0.004, 0.2), 2, 2)
muC <- c(3,2)
SigmaC <- matrix(c(0.2, 0.004, 0.004, 0.2), 2, 2)

train <- rbind(mvrnorm(NTR, muA, SigmaA), mvrnorm(NTR, muB, SigmaB), mvrnorm(NTR, muC, SigmaC))
test <- rbind(mvrnorm(NTE, muA, SigmaA), mvrnorm(NTE, muB, SigmaB), mvrnorm(NTE, muC, SigmaC))

train <- cbind(train, matrix(runif(G * NTR * (NF - 2), 0, 4), nrow = G * NTR, ncol = (NF-2)))
test <- cbind(test, matrix(runif(G * NTE * (NF - 2), 0, 4), nrow = G * NTE, ncol = (NF-2)))

wtr <-  as.factor(rep(1:G, each = NTR))
wte <-  as.factor(rep(1:G, each = NTE))
pairs(train, col = wtr)




library(e1071)

evaluate <- function(th){ 
    if (sum(th) == 0)return(0)             
    model <- svm(train[ ,th==1], wtr , gamma = 0.1)
    pred <- predict(model, test[ ,th==1])
    csRate <- sum(pred == wte)/NTE 
    penalty <- (NF - sum(th))/NF 
    return(csRate + penalty)
}  
 
res <- tabuSearch(size = NF, iters = 50, objFunc = evaluate, config = matrix(1,1,NF),
listSize = 5, nRestarts = 4) 


plot(res)
plot(res, "tracePlot")

summary(res, verbose = TRUE)

## End(Not run)

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