Class Imbalance

Calculate class imbalance as given by: $$I = K\cdot\sum_{i=1}^K (n_i/N - 1/K)^2$$ where \(K\) is the number of classes, and \(n_i\) is the number of instances of class \(i\)

Usage

class_imbalance(x)

Arguments

x

Vector, factor: Outcome.

Value

Numeric.

Author

EDG

Examples

# iris is perfectly balanced
class_imbalance(iris[["Species"]])
#> [1] 0
# Simulate imbalanced outcome
x <- factor(sample(c("A", "B"), size = 500L, replace = TRUE, prob = c(0.9, 0.1)))
class_imbalance(x)
#> [1] 0.595984