Convert mean/dispersion parameterizations — calibrate

calibrate_distribution() inverts the mean and dispersion parameterization used by the formula/variance specification columns into the shape parameters base R's samplers take. For a mean and a variance, and for the wider catalogue, use calibrate_moments().

Usage

calibrate_distribution(
  distribution = c("beta", "gamma", "negative_binomial"),
  mean,
  dispersion
)

Arguments

distribution: Beta, gamma, or negative-binomial distribution.
mean: Distribution mean.
dispersion: Beta precision or gamma/negative-binomial dispersion.

Value

A base data.frame with one row per input value and parameter, and columns distribution, mean, dispersion, parameter and value.

Examples

calibrate_distribution("beta", mean = 0.4, dispersion = 8)
#>   distribution mean dispersion parameter value
#> 1         beta  0.4          8    shape1   3.2
#> 2         beta  0.4          8    shape2   4.8
calibrate_distribution("gamma", mean = 10, dispersion = 0.5)
#>   distribution mean dispersion parameter value
#> 1        gamma   10        0.5     shape   2.0
#> 2        gamma   10        0.5      rate   0.2
calibrate_distribution("negative_binomial", mean = 5, dispersion = 0.4)
#>        distribution mean dispersion parameter     value
#> 1 negative_binomial    5        0.4      size 2.5000000
#> 2 negative_binomial    5        0.4      prob 0.3333333