R/bisect.R

In ppham27/setsim: Software tool for the visualization of confidence regions in statistical models

bisect <- function(fn, a, b,
                   tol=0.00001, error=0.0001, decimal=5,
                   input, VZ, c_value) {
  fn1 <- function(x) {
    fn(x,...)
  }
  Ans <- 0
  diff <- 10
  old_p <- (a+b)/2
  if (fn(a,input,VZ,c_value)==0) {
    Ans <- a
  } else if (fn(b,input,VZ,c_value)==0) {
    Ans <- b
  } else {
    while (diff >= tol) {
      if ((b-a)/2 < error) {
        Ans <- old_p
      } else if (fn(a,input,VZ,c_value)*fn(old_p,input,VZ,c_value) > 0) {
        a <- old_p
      }
      else {
        b <- old_p
      }
      new_p <- (a + b)/2
      diff <- abs(fn(new_p, input, VZ, c_value) - fn(old_p,input, VZ, c_value))
      old_p <- new_p
      Ans <- old_p
    }
    round(Ans, decimal)
  }
}