Description

Utilities for the logitnormal distribution in R

• Density, distribution, quantile and random generation function.

• Estimation of the mode and the first two moments.

• Estimation of distribution parameters from observations.

Details

The package provides the main distribution functions:

• density dlogitnorm,

• distribution plogitnorm,

• quantile qlogitnorm, and

• random generation function rlogitnorm.

Transformation functions

• (0,1) -> (-Inf,Inf): logit

• (-Inf,Inf) -> (0,1): invlogit

Moments and mode

• Expected value and variance: momentsLogitnorm

• Mode: modeLogitnorm

Estimating parameters

• from mode and upper quantile: twCoefLogitnormMLE

• from mode and constraint to be unimodal and maximally flat: twCoefLogitnormMLEFlat

• from median and upper quantile: twCoefLogitnorm

• from expected value, i.e. mean and upper quantile: twCoefLogitnormE

• from a confidence interval which is symmetric at normal scale: twCoefLogitnormCi

• from prescribed quantiles: twCoefLogitnormN

Have a look at the package vignettes.

Author(s)

Thomas Wutzler

References

Frederic, P. & Lad, F. (2008) Two Moments of the Logitnormal Distribution. Communications in Statistics-Simulation and Computation, 37, 1263-1269