pgam.likelihood {pgam} | R Documentation |
This is the log-likelihood function that is passed to optim
for likelihood maximization.
pgam.likelihood(par, y, x, offset, fperiod, env = parent.frame())
par |
vector of parameters to be optimized |
y |
observed time series which is the response variable of the model |
x |
observed explanatory variables for parametric fit |
offset |
model offset. Just like in GLM |
fperiod |
vector of seasonal factors to be passed to pgam.par2psi |
env |
the caller environment for log-likelihood value to be stored |
Log-likelihood function of hyperparameters omega and β is given by
log L(omega,β)=sum_{t=tau+1}^{n}{log Γ(a_{t|t-1}+y_{t})-log y_{t}!-
log Γ(a_{t|t-1})+a_{t|t-1}log b_{t|t-1}-(a_{t|t-1}+y_{t})log (1+b_{t|t-1})}
where a_{t|t-1} and b_{t|t-1} are estimated as it is shown in pgam.filter
.
List containing log-likelihood value, optimum linear predictor and the gamma parameters vectors.
This function is not intended to be called directly.
Washington Leite Junger wjunger@ims.uerj.br and Antonio Ponce de Leon ponce@ims.uerj.br
Harvey, A. C., Fernandes, C. (1989) Time series models for count data or qualitative observations. Journal of Business and Economic Statistics, 7(4):407–417
Harvey, A. C. (1990) Forecasting, structural time series models and the Kalman Filter. Cambridge, New York
Junger, W. L. (2004) Modelo Poisson-Gama Semi-Parametrico: Uma Abordagem de Penalizacao por Rugosidade. MSc Thesis. Rio de Janeiro, PUC-Rio, Departamento de Engenharia Eletrica