R/TypeOne.R

In MatheMax/OptReSample: Computing Optimal Adaptive Designs

#' Compute the type I error
#'
#' \code{type_one} computes the type I error approximately if the \code{c_2}-function is approximated via a set of splines.
#'
#' Note that nodes and c_2 have to be of the same length.
#'
#' @param parameters Parameters (alpha, power, standardized effect) whith which you want to build your design
#' @param cf Boundary for stopping for futility after the first stage
#' @param ce Boundary for stopping for efficacy after the first stage
#' @param nodes Nodes for the c_2-function
#' @param c2 Corresponding c_2-values
#'
#' @export

type_one <- function(parameters, cf, ce, nodes, c2){
  f <- splinefun(nodes, c2)
  N = 12
  h = (ce - cf) / N
  x = seq(cf, ce,h)
  alpha=c(1, rep (2,(N-1)), 1)

  # w = c(x, alpha)
  to <- function(w){
    w[2] * pnorm(f(w[1])) * dnorm(w[1])
  }

  y <- apply(cbind(x,alpha), 1, to)


  p <- (h/2) * sum(y)
  p <- 1 - pnorm(cf) - p
  return(p)
}