mom_gamma: Method of moments for gamma distribution

In hesim: Health Economic Simulation Modeling and Decision Analysis

Method of moments for gamma distribution

Description

Compute the shape and scale (or rate) parameters of the gamma distribution using method of moments for the random variable of interest.

Usage

mom_gamma(mean, sd, scale = TRUE)

Arguments

mean	Mean of the random variable.
sd	Standard deviation of the random variable.
scale	Logical. If TRUE (default), then the scale parameter is returned; otherwise, the rate parameter is returned.

Details

If μ is the mean and σ is the standard deviation of the random variable, then the method of moments estimates of the parameters shape = α > 0 and scale = θ > 0 are:

θ = \frac{σ^2}{μ}

and

α = \frac{μ}{θ}

The inverse of the scale parameter, β = 1/θ, is the rate parameter.

Value

If scale = TRUE, then a list containing the parameters shape and scale; otherwise, if scale = FALSE, then a list containing the parameters shape and rate.

Examples

mom_gamma(mean = 10000, sd = 2000)
# The function is vectorized.
mom_gamma(mean = c(8000, 10000), sd = c(1500, 2000))

hesim documentation built on Sept. 4, 2022, 1:06 a.m.