garchSim {fGarch}R Documentation

Univariate GARCH Time Series Simulation

Description

Simulates an univariate GARCH time series model.

Usage

garchSim(model = list(omega = 1.0e-6, alpha = 0.1, beta = 0.8), n = 100, 
    n.start = 100, presample = NULL, cond.dist = c("rnorm", "rged", "rstd", 
    "rsnorm", "rsged", "rsstd"), rseed = NULL)

Arguments

cond.dist a character string naming the desired conditional distribution. Valid values are "dnorm", "dged", "dstd", "dsnorm", "dsged", "dsstd". The default value is the normal distribution.
model a list of GARCH model parameters:
omega - the constant coefficient of the variance equation, by default 1e-6;
alpha - the value or vector of autoregressive coefficients, by default 0.1, specifying a model of order 1;
beta - the value or vector of variance coefficients, by default 0.8, specifying a model of order 1;
The optional values for the linear part are:
mu - the mean value, by default 0;
ar - the autoregressive ARMA coefficients, by default 0;
ma - the moving average ARMA coefficients, by default 0.
The optional parameters for the conditional distributions are:
skew - the skewness parameter (also named xi), by default 0.9, effective only for the "dsnorm", the "dsged", and the "dsstd" skewed conditional distributions;
shape = the shape parameter (also named nu), by default 2 for the "dged" and "dsged", and by default 4 for the "dstd" and "dsstd" conditional distributions.

Note, the default model specifies Bollerslev's GARCH(1,1) model with normal distributed innovations.
n length of output series, an integer value. An integer value, by default n=100.
n.start length of "burn-in" period, by default 100.
presample a numeric three column matrix with start values for the series, for the innovations, and for the conditional variances. For an ARMA(m,n)-GARCH(p,q) process the number of rows must be at least max(m,n,p,q), longer presamples are cutted.
rseed single integer argument, the seed for the intitialization of the random number generator for the innovations.

Value

returns an objects of class ts atrributed with an appropriate specification structure as returned by the function garchSpec.

Author(s)

Diethelm Wuertz for the Rmetrics R-port.

Examples

## garchSpec -
   spec = garchSpec()
   spec

## garchSim -
   x = garchSim(model = spec@model, n = 500)
   head(x) 

[Package fGarch version 260.72 Index]