PreMean <- matrix(ncol=3, nrow=2, byrow=TRUE)
PreMean[1, ] <- c(1, -1, 0)
PreMean[2, ] <- c(-0.8, 0, 0.8)
PreZeta <- c(0.4, 1.8, 1)

GenExpression <- function(x, cancertype, sdv) {
    rnorm(1, PreMean[x,cancertype], sdv)
}

GenSurvival <- function(funtype, cancertype, x1, x2, cancerprob) {
#    rm(.Random.seed)
	 S <- runif(1, 0, 1)
	 
    if(cancertype==1) {  h <- 0.3*x1 + 0.4*x2 - 0.1  }
    if(cancertype==2) {  h <- 0.5*(x1-x2)^2 + 1      }
	 if(cancertype==3) {  h <- 0.006*x1^3 - 0.2*x2    }
	 
	 if(funtype=="1") {  -(log(S)/exp(-h))  }
	 
	 #survival function is Weibull
	 exp((-log(S)/exp(-h))^(1/PreZeta[cancertype]))
}