spass (version 1.2)

estimcov: Estimation of simulation parameters

Description

estimcov estimates the covariance matrix and dropout rates given a dataset and observation-times

Usage

estimcov(data, Time, Startvalues = c(3, 0.5, 1), stepwidth = c(0.001, 0.001,
  0.001), maxiter = 10000, lower = c(1e-04, 1e-04, 1e-04), upper = c(Inf,
  5, 3))

Arguments

data

matrix with the dataset which is used to estimate the covariance and dropout structure.

Time

vector with observation-times.

Startvalues

vector with starting values for variance, rho and theta respectively.

stepwidth

vector describing the step length of previously mentioned values.

maxiter

maximum amount of iterations

lower

vector with minimum for the parameters described in Startvalues

upper

vector with maximum for the parameters described in Startvalues

Value

estimcov returns a list with two entries. In the first the parameters variance, rho and theta are returned and in the second a vector with the dropout-rate is returned.

Details

This function is designed to estimate the variance, rho and theta and a vector with the dropout rate in the data.

Examples

# NOT RUN {
# First generate a dataset with 200 patients, rho =0.25 and tau = 0.5 and
# then estimate the parameters using estimcov.

set.seed(2015)
dataset <- r.gee.1subgroup(n=200, reg=list(c(0,0,0,0.1),c(0,0,0,0.1)), sigma=c(3,2.5),
  tau=0.5, rho=0.25, theta=1, k=1.5, Time=c(0:5), OD=0)

estimations <- estimcov(data=dataset,Time=c(0:5))
estimations[[1]]
estimations[[2]]

# }