Alternative approach to 4-digit brain teaser...

4d_brain_teaser.R

# alternative approach to teaser game

library(gtools)
library(lattice)

# get data set
load(url('http://www.babelgraph.org/data/brain_teaser_data.Rdata'))
ls()

# set operators
ops <- c('+','-','*','/')

# get all possible operator combinations 4^3=64
combos <- permutations(n=4,r=3,v=ops,repeats.allowed=TRUE)

# define function to calculate error from operator combos

CalcError <- function (op) {
	
	# generate model from operators and apply to each data set
	
	rr <- apply(series, 1, function(x) {
                        mycode <- paste('abs(',x[1],op[1],x[2],op[2],x[3],op[3],x[4],')-',x[5])
                        eval(parse(text=mycode))
                    })
	
	return (sum(abs(unlist(rr))))
}

# check validity of each model

model.error <- apply(combos,1,CalcError)

# review results

results <- data.frame(	model=as.character(apply(combos,1,
			     function(x) paste(x[1],x[2],x[3],sep=''))),
			error = model.error)

summary(results)

densityplot(~error,results)

dotplot(model~error,results)