Entropy for a given split of a categorical variable

Source: R/entropy.R

Calculates the entropy of a categorical variable for a given split (threshold) value of a numeric variable.

entropy(x, group, thres)

Arguments

x

A numeric vector
group

Categorical variable
thres

Threshold value to use for the split

Value

A data frame with entropy before and after the split, as well as the gain and gain percent

References

Kuhn, M. & Johnson, K. (2013). Applied Predictive Modeling. Springer.

Witten, I. H., Frank, E. & Hall, M. A. (2011). Data Mining: Practical Machine Learning Tools and Techniques. Elsevier.

Examples

entropy(mtcars$mpg, mtcars$cyl, 15)

#>  ent.init ent.split ent.gain ent.gain.perc
#>      1.53      1.32     0.21          13.7
entropy(mtcars$mpg, mtcars$cyl, 21)

#>  ent.init ent.split ent.gain ent.gain.perc
#>      1.53     0.758    0.772          50.5
entropy(mtcars$mpg, mtcars$cyl, 25)

#>  ent.init ent.split ent.gain ent.gain.perc
#>      1.53      1.18     0.35          22.9