create.grid {surveillance}R Documentation

Computes a matrix of initial values

Description

For a given model and a list of parameters specified as param = c(lower,upper,length), create.grid creates a grid of initial values for algo.hhh.grid. The resulting matrix contains all combinations of the supplied parameters which each are a sequence of length length from lower to upper. Note that the autoregressive parameters λ, phi and the overdispersion parameter psi must be positive. Only one sequence of initial values is considered for the autregressive, endemic and overdispersion parameters to create the grid, e.g. initial values are the same for each one of the seasonal and trend parameters.

Usage

create.grid(disProgObj, control, params = list(epidemic = c(0.1, 0.9, 5),
   endemic=c(-0.5,0.5,3), negbin = c(0.3, 12, 10)))

Arguments

disProgObj object of class disProg
control specified model
params list of parameters: param=c(lower,upper,length)
    epidemic
    autoregressive parameters λ and phi.
    endemic
    trend and seasonal parameters β,gamma_j.
    negbin
    overdispersion parameter for negative binomial model psi.

Value

matrix matrix with gridSize starting values as rows

Author(s)

M. Paul

See Also

algo.hhh.grid

Examples

# simulate data
set.seed(123)
disProgObj <- simHHH(control = list(coefs = list(alpha =-0.5, gamma = 0.4,
                     delta = 0.6)),length=300)$data

# consider the model specified in a control object for algo.hhh.grid
cntrl1 <- list(lambda=TRUE, neighbours=TRUE, 
               linear=TRUE, nseason=1)
cntrl2 <- list(lambda=TRUE, negbin="single")

# create a grid of initial values for respective parameters
grid1 <- create.grid(disProgObj, cntrl1, params = list(epidemic=c(0.1,0.9,3), 
                     endemic=c(-1,1,3)))
grid2 <- create.grid(disProgObj, cntrl2, params = list(epidemic=c(0.1,0.9,5), 
                     negbin=c(0.3,12,10)))


[Package surveillance version 1.0-3 Index]