Description Usage Arguments Value Details References Examples
Function to calculate the shape, α, and scale, θ, (or rate, β) parameters of a gamma distribution based on the method of moments (MoM) using the mean μ and standard deviation σ of the random variable of interest.
1 | gamma_params(mu, sigma, scale = TRUE)
|
mu |
scalar with the mean of the random variable. |
sigma |
scalar with the standard deviation of the random variable. |
scale |
logical variable indicating scale parameterization of the gamma distribution (Default is TRUE). If FALSE, rate parameterization is retrieved |
A list contianing the following:
shape Shape parameter of gamma distribution
scale Scale parameter of gamma distribution (If scale=TRUE)
rate Rate parameter of gamma distribution (If scale=FALSE)
Based on method of moments. If μ is the mean and σ is the standard deviation of the random variable, then the the shape, α, scale, θ, and rate, β, parameters are computed as follows
α=\frac{μ^2}{σ^2},
θ = \frac{σ^2}{μ}
and
β = \frac{μ}{σ^2}
Gamma distribution. (2018, February 7). In Wikipedia, The Free Encyclopedia. Retrieved 17:23, February 11, 2018, from https://en.wikipedia.org/w/index.php?title=Gamma_distribution&oldid=824541785
1 2 3 4 5 6 | mu <- 2
sigma <- 1
# Scale specification
gamma_params(mu, sigma)
# Rate specification
gamma_params(mu, sigma, scale = FALSE)
|
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