gamma_params {dampack} | R Documentation |
Function to calculate the shape, \alpha
, and scale, \theta
, (or rate, \beta
)
parameters of a gamma distribution based on the method of moments (MoM)
using the mean \mu
and standard deviation \sigma
of the random
variable of interest.
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 \mu
is the mean and
\sigma
is the standard deviation of the random variable, then the
the shape, \alpha
, scale, \theta
, and rate, \beta
, parameters are computed
as follows
\alpha=\frac{\mu^2}{\sigma^2},
\theta = \frac{\sigma^2}{\mu}
and
\beta = \frac{\mu}{\sigma^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
mu <- 2
sigma <- 1
# Scale specification
gamma_params(mu, sigma)
# Rate specification
gamma_params(mu, sigma, scale = FALSE)