rgsm: Simulating realizations from the gamma shape mixture model
Description
Simulates realizations from a gamma shape mixture (GSM) model with probability density function given by
$$f(x,{\Theta}) = \sum_{j=1}^{K}\omega_j \frac{\beta^j}{\Gamma(j)} x^{j-1} \exp\bigl( -\beta x\bigr),$$
where \(\Theta=(\omega_1,\dots,\omega_K, \beta)^T\) is the parameter vector and known constant \(K\) is the number of components. The vector of mixing parameters is given by \(\omega=(\omega_1,\dots,\omega_K)^T\) where \(\omega_j\)s sum to one, i.e., \(\sum_{j=1}^{K}\omega_j=1\). Here \(\beta\) is the rate parameter that is equal for all components.
Usage
rgsm(n, omega, beta)
Arguments
n
Number of requested random realizations.
omega
Vector of the mixing parameters.
beta
The rate parameter.
Value
A vector of length n, giving random generated values from GSM model.
References
S. Venturini, F. Dominici, and G. Parmigiani, 2008. Gamma shape mixtures for heavy-tailed distributions, The Annals of Applied Statistics, 2(2), 756<U+2013>776.