shannonEntropy {aqp}

Shannon Entropy

Description

A very simple implementation of Shannon entropy.

Usage

shannonEntropy(x, b = 2)

Arguments

x

vector of probabilities (0,1), must sum to 1, should not contain NA

b

logarithm base

Details

0s are automatically removed by na.rm = TRUE, as (0 * log(0) = Nan)

Value

A single numeric value.

Note

When b = length(x) the result is the normalized Shannon entropy of (Kempen et al, 2009).

References

Kempen, Bas, Dick J. Brus, Gerard B.M. Heuvelink, and Jetse J. Stoorvogel. 2009. "Updating the 1:50,000 Dutch Soil Map Using Legacy Soil Data: A Multinominal Logistic Regression Approach." Geoderma 151: 311-26. doi:10.1016/j.geoderma.2009.04.023

Shannon, Claude E. (July-October 1948). "A Mathematical Theory of Communication". Bell System Technical Journal. 27 (3): 379-423. doi:10.1002/j.1538-7305.1948.tb01338.x

Examples

# a very simple example
p <- c(0.25, 0.25, 0.4, 0.05, 0.05)

shannonEntropy(p)