soundgen (version 3.0.0)

getEntropy: Entropy

Description

Returns Wiener or Shannon entropy of an input vector such as the spectrum of a sound. Non-positive input values are converted to a small positive number (convertNonPositive). If all elements are zero, returns NA.

Usage

getEntropy(
  x,
  type = c("wiener", "shannon"),
  normalize = FALSE,
  convertNonPositive = 1e-10
)

Value

The entropy of input vector as a single number.

Arguments

x

vector of positive floats

type

'shannon' for Shannon (information) entropy, 'wiener' for Wiener entropy

normalize

if TRUE, Shannon entropy is normalized by the length of input vector to range from 0 to 1. It has no effect on Wiener entropy

convertNonPositive

occasional non-positive values are converted to convertNonPositive (if all inputs are non-positive, entropy = NA)

Examples

# Here are four simplified power spectra, each with 9 frequency bins:
s = list(
  onePeak = c(rep(0, 4), 1, rep(0, 4)),         # a single peak in spectrum
  harmonics = c(0, 0, 1, 0, 0, .75, 0, 0, .5),  # perfectly periodic, with 3 harmonics
  silent = rep(0, 9),                           # a silent frame
  noise = rep(1, 9)                             # white noise
)

# Wiener entropy is ~0 for periodic, NA for silent, 1 for white noise
lapply(s, function(x) round(getEntropy(x), 2))

# Shannon entropy is ~0 for periodic with a single harmonic, moderate for
# periodic with multiple harmonics, NA for silent, highest for white noise
lapply(s, function(x) round(getEntropy(x, type = 'shannon'), 2))

# Normalized Shannon entropy - same but forced to be 0 to 1
lapply(s, function(x) round(getEntropy(x,
  type = 'shannon', normalize = TRUE), 2))