R/bsearch.R

In ldbounds: Lan-DeMets Method for Group Sequential Boundaries

"bsearch" <- function(last,nints,i,pd,stdv,ya,yb){
    tol <- 10^(-7)
    del <- 10
    uppr <- yb[i-1]
    q <- qp(uppr,last,nints[i-1],ya[i-1],yb[i-1],stdv)
    while (abs(q-pd) > tol){
      del <- del/10
      incr <- 2*as.integer(q > pd+tol)-1
      j <- 1
      while (j <= 50){
        uppr <- uppr+incr*del
        q <- qp(uppr,last,nints[i-1],ya[i-1],yb[i-1],stdv)
        if ({abs(q-pd) > tol}&{j==50}){
          stop("Error in search: not converging")
        }
        else if ({{incr==1}&{q <= pd+tol}}|{{incr==-1}&{q >= pd-tol}}){
          j <- 50
        }
        j <- j+1
      }
    }
    ybval <- uppr
    return(ybval)
  }