Returns the entropy of the distribution defined by
group.
Usage
entropy(data, group, weight = NULL, base = exp(1))Arguments
- data
A data frame.
- group
A categorical variable or a vector of variables contained in
data.- weight
Numeric. (Default
NULL)- base
Base of the logarithm that is used in the entropy calculation. Defaults to the natural logarithm.
Examples
d <- data.frame(cat = c("A", "B"), n = c(25, 75))
entropy(d, "cat", weight = "n") # => .56
#> [1] 0.5623351
# this is equivalent to -.25*log(.25)-.75*log(.75)
d <- data.frame(cat = c("A", "B"), n = c(50, 50))
# use base 2 for the logarithm, then entropy is maximized at 1
entropy(d, "cat", weight = "n", base = 2) # => 1
#> [1] 1