Calculates perplexity

Calculates the perplexity of a vector of (log-)probabilities.

Usage

perplexity_calc(x, na.rm = FALSE, log.p = TRUE)

Arguments

x

A vector of log-probabilities.

na.rm

Should missing values (including NaN) be removed?

log.p

If TRUE (default), x are assumed to be log-transformed probabilities with base e, if FALSE x are assumed to be raw probabilities, alternatively log.p can be the base of other logarithmic transformations.

Value

The perplexity.

Details

If x are raw probabilities (NOT the default), then perplexity is calculated as follows:

$$\left(\prod_{n} x_n \right)^\frac{1}{N}$$

See also

Other general functions: set_cache_folder()

Examples

probs <- c(.3, .5, .6)
perplexity_calc(probs, log.p = FALSE)
#> [1] 2.231443
lprobs <- log(probs)
perplexity_calc(lprobs, log.p = TRUE)
#> [1] 2.231443