preprocess.dataset = function()
{   
    xls.file = "CTG.xls"
    
    wk      = loadWorkbook(file.path(orig.dir, xls.file))
    dataset = readWorksheet(wk, sheet = "Raw Data")
    
    dataset = dataset %>% select(LB:FS, NSP, -c(DS, DR)) %>% 
        filter(complete.cases(.)) %>%
        mutate(LB       = as.integer(LB),
               AC       = as.integer(AC),
               FM       = as.integer(FM),
               UC       = as.integer(UC),
               ASTV     = as.integer(ASTV),
               ALTV     = as.integer(ALTV),
               DL       = as.integer(DL),
               DP       = as.integer(DP),
               Width    = as.integer(Width),
               Min      = as.integer(Min),
               Max      = as.integer(Max),
               Nmax     = as.integer(Nmax),
               Nzeros   = as.integer(Nzeros),
               Mode     = as.integer(Mode),
               Mean     = as.integer(Mean),
               Median   = as.integer(Median),
               Variance = as.integer(Variance),
               Tendency = factor(Tendency, levels = c(-1, 0, 1), 
                                 ordered = TRUE),
               A        = factor(A),
               B        = factor(B),
               C        = factor(C),
               D        = factor(D),
               E        = factor(E),
               AD       = factor(AD),
               DE       = factor(DE),
               LD       = factor(LD),
               FS       = factor(FS),
               NSP      = factor(replace(NSP, NSP == 2, 3)))

    return(dataset)
}