saferoot: Improved One Dimensional Root (Zero) Finding
In abnormally-distributed/cvreg: Cross Validation and Robust Estimation Utilities

a "safe" version of uniroot() searches for a root (that is, zero) of the function f with respect to its first argument. "safe" means searching for the correct interval = c(lower,upper) if sign(f(x)) does not satisfy the requirements at the interval end points This function was adapted from the copula package.

saferoot(
  f,
  interval,
  ...,
  lower = min(interval),
  upper = max(interval),
  f.lower = f(lower, ...),
  f.upper = f(upper, ...),
  Sig = NULL,
  check.conv = FALSE,
  tol = 0.001,
  maxiter = 2500,
  trace = 0
)

`f`	the function for which the root is sought.
`interval`	a vector containing the end-points of the interval to be searched for the root.
`...`	additional named or unnamed arguments to be passed to f
`lower`	the lower end point of the interval to be searched
`upper`	the upper end point of the interval to be searched
`f.lower`	the same as f(lower)
`f.upper`	the same as f(upper)
`Sig`	desired sign of f(upper), or NULL
`check.conv`	logical indicating whether a convergence warning of the underlying uniroot should be caught as an error and if non-convergence in maxiter iterations should be an error instead of a warning.
`tol`	the desired accuracy (convergence tolerance). defaults to 1e-3.
`maxiter`	the maximum number of iterations. defaults to 2500.
`trace`	integer number; if positive, tracing information is produced. Higher values giving more details.