R/pmt.R

In hongqi0314/PRAuto.PMML: User defined functions to output a PMML file that is to be implemented in S1

#' Calculate monthly payment
#'
#' Calculate payment based on APR, Amount Financed and Term (in months).
#' Should yield same results as Excel's "PMT" function
#'
#' @param r A float number representing APR.
#' @param p A float number representing amount financed
#' @param n An integer representing term in months
#'
#' @return A float number representing monthly payment
#' @export
#'
#' @examples
#' alf_payment <- pmt(0.17, 30000, 72)
pmt <- function(r, p, n){
  rate <- r / 12
  cumu <- (1 + rate) ^ n
  return( p * ( (rate * cumu) / (cumu - 1) ) )
}