R/simCov.R

In simfms: Simulation of clustered multi-state data

################################################################################
#  Simulation of covariates                                                    #
################################################################################
#                                                                              #
#  Simulates the covariates for a frailty multi-state simulation model         #
#                                                                              #
#  Its parameters are                                                          #
#   - covs      : the list of covariates to simulate. Its elements must be     #
#                 nameOfCovariate = simulationfunction                         #
#   - nsim      : the number of subjects to simulate                           #
#                                                                              #
#                                                                              #
#   Date: February, 13, 2012                                                   #
#   Last modification on: March, 29, 2012                                      #
################################################################################

simCov <- function(covs, 
                   nsim=3000){
  if (is.null(nsim))
    stop("Please, set the number of subjects 'nsim'!")
  if (is.null(cov)) 
    stop("Please, set the covariates object 'covs'!")
  if (!is.list(covs)) 
    stop("The covariates object 'covs' must be a list!")
  if (is.null(names(covs)) || ""%in%names(covs))
    stop("All the names of covariates must be specified as
         covs=list(name1=..., ..., nameN=...)")
  
  res <- NULL
  
  for (i in 1:length(covs)){
    if (length(covs[[i]])!=1) 
      stop(paste("The covariate '", names(covs)[i],
                 "' has length ", length(covs[[i]]), " instead of 1!", sep=""))
    if (!is.function(covs[[i]])) 
      stop(paste("The element '", names(covs)[i],
                 "' of the covariates list 'covs' is not a function!", sep=""))
    
    cat(paste("Simultaion of covariate '", names(covs)[i],"'...\n", sep=""))
    res[[names(covs)[[i]]]] <- covs[[i]](nsim)
  }
  return(as.data.frame(res))
}