to_shape_rate_gamma: Parameter Conversion for Gamma Distribution
Description
The function to_shape_rate_gamma converts the mean and standard deviation to the shape and rate
Usage
to_shape_rate_gamma(mu, sd)
Value
a list of two items
alpha
a vector of the shapes of gamma distributions
lambda
a vector of the rates of gamma distributions
Arguments
mu
a numeric vector representing the means of gamma distributions
sd
a numeric vector representing the standard deviations of gamma distributions.
mu and sd should have the same length.
Details
The purpose of this function is to convert the parameterization of gamma distribution in the form of
mean and standard deviation to the form of shape and rate. It can be used for specifying the initial
values for the EM algorithm when the first-hand initial values are in the form of mean and standard
deviation from K-means clustering algorithm.