R/qp.R

In ldbounds: Lan-DeMets Method for Group Sequential Boundaries

"qp" <- function(xq,last,nints,yam1,ybm1,stdv){
    hlast <- (ybm1-yam1)/nints
    grid <- seq(yam1,ybm1,length=nints+1)
    fun <- last*pnorm(grid,mean=xq,sd=stdv)
    qp <- 0.5*hlast*(2*sum(fun)-fun[1]-fun[length(fun)]) # This is "trap"
    return(qp)
  }