R/EPP_singleperiod.R

In haythamomar/inventorize: Inventory Analytics and Cost Calculations

#' EPP_singleperiod
#'
#' Expected profit from a newsvendor model based on a poisson distribution.
#'
#' calculating expected profit for a newsvendor model. based on assumed poisson distribution demand.
#'

#' @param quantity numeric,quantity to be ordered during season.
#' @param lambda numeric,  mean of the demand based on poisson distribution.
#'
#' @param  p  numeric,selling price of the SKU
#' @param  c  numeric,cost of the SKU
#' @param  g  numeric,,salvage or discounted value if sold after season,if there is no salvage , zero is placed in the argument.
#' @param  b numeric, peanlity cost of not satisfying demand if any, if not, zero is placed in the argument.
#' @param  na.rm A logical indicating whether missing values should be removed
#'
#' @return a dataframe that contains calculations of the  expected profit from a newsvendor model based on poisson distribution.
#'@import stats

#' @export
#'
#' @example
#'
#'  EPP_singleperiod(quantity=40149,lambda= 32000,P=24,C=10.9,g=7,b=0,na.rm=TRUE)
#'
#' @author "haytham omar  email: <h.omar5942@gmail.com>"
#' @note this is the first version of the inventorize package, all the fucntions are common knowlege for supply chain without
#' any academic contribution from my side, the aim is to facilitate and ease much of the bookkeeping that is endured during stock analysis.
#'the package relies heavily on the studies that I had in the MIT micromasters program for supply chain.








EPP_singleperiod<-function(quantity,lambda,p,c,g,b,na.rm=TRUE){


  eus<- lambda-(lambda*ppois(quantity-1,lambda))-quantity*(1-ppois(quantity,lambda))
  expectedprofit<- (p-g+b)*(quantity*ppois(quantity-1,lambda))- (quantity*ppois(quantity,lambda))
  + (p-c+b)*quantity-(b*lambda)
  expectedunitsold<- lambda*ppois(quantity-1,lambda)+quantity*(1-ppois(quantity,lambda))
  CDF<- ppois(quantity,lambda)
  return(data.frame(quantity=quantity,lambda=lambda,lost_sales=eus,
                    expected_sales=expectedunitsold,expectedprofit=expectedprofit,CDF=CDF))
}

EPP_singleperiod(5,2.6,24,10.9,7,0,na.rm=TRUE)