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.
Details
If x are raw probabilities (NOT the default),
then perplexity is calculated as follows:
$$\left(\prod_{n} x_n \right)^\frac{1}{N}$$
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
