cut function is used to create the factor.bin.var(x, bins = 4, method = c("intervals", "proportions", "natural"),
labels = FALSE)"intervals" for equal-width bins;
"proportions" for equal-count bins;
"natural" for cut points between bins to be determined
by a k-means clustering.FALSE, numeric labels will be used for the factor levels;
if NULL, the cut points are used to define labels; otherwise a character
vector of level names.cut, kmeans.