R/ROR.R

In bips-hb/pvm: PharmacoVigilance Methods

#' Reporting Odds Ratio (ROR)
#'
#' Determines the ROR for a collection of 2 x 2 tables of the form:
#' \tabular{lcc}{
#'    \tab event \tab not event\cr
#'   drug \tab \code{a} \tab \code{c}\cr
#'   not drug \tab \code{b} \tab \code{d}
#' }
#' In case the parameter \code{alpha} is set, it returns
#' the lower endpoint of the \eqn{100(1 - \alpha)} percent confidence interval.
#'
#' @template standardParams
#' @template alphaParam
#' 
#' @return The ROR or the lower endpoint of the confidence interval of the ROR
#' @export
ROR <- function(a, b, c, d, alpha = NULL) {
  ror <- (a * d) / (b * c)
  if (is.null(alpha)) {
    return(ror)
  } else{
    phi <- qnorm(1.0 - alpha / 2)
    return(exp(log(ror) - phi * sqrt((1 / a) + (1 / b) + (1 / c) + (1 / d))))
  }
}