R/CalcPPV.R

In wlktan/surrogateSampling: Functions to conduct surrogate guided sampling designs

#' CalcPPV
#'
#' This function returns the positive predictive value of a binary test
#' @param sens numeric; sensitivity of the binary test
#' @param spec numeric; specificity of the binary test
#' @param prev numeric; prevalence of the finding
#' @keywords ppv
#' @export
#' @return the positive predicted value of a binary test
#' @examples
#' CalcPPV(0.2,0.8,0.13)

CalcPPV <- function(sens,spec,prev){ 
  # Checks for valid input
  stopifnot(sens >= 0 & sens <= 1)
  stopifnot(spec >= 0 & spec <= 1)
  stopifnot(prev >= 0 & prev <= 1)
  
  ppv <- (sens*prev)/(sens*prev + (1-spec)*(1-prev))
  return(ppv)
}