R/PlotMethods.R

In antitrust: Tools for Antitrust Practitioners

#' @title Methods For Calculating Upwards Pricing Pressure Index (Bertrand)
#' @name Plot-Methods
#' @docType methods
#'
#' @aliases plot,Bertrand-method
#'
#' @description Use \code{\link[ggplot2]{ggplot}} to plot pre- and post-merger demand, marginal cost and equilibria.
#' \sQuote{scale} controls the amount above marginal cost and below equilbrium price that is plotted.
#'
#' @param x Used only in plot method. Should always be set equal to object.
#' @param scale The proportion below marginal cost and above equilbrium price that should be plotted. Default is .1.
#'
#' @include OutputMethods.R
#' @keywords methods
NULL

##plot method
#'@rdname Plot-Methods
#'@export
setMethod(
  f= "plot",
  signature= "Bertrand",
  definition=function(x,scale=.1){
    object=x
    nprods=length(object@labels)
    pricePre=object@pricePre
    pricePost=object@pricePost

    if(all(is.na(pricePre)) ||
       all(is.na(pricePost))){
      stop("'pricePre' or 'pricePost' are all NA")
    }

    mcPre=object@mcPre
    mcPost=object@mcPost
    labels=object@labels
    isParty <- rowSums( abs(object@ownerPost - object@ownerPre))>0
    isParty <- ifelse(isParty,"*","")
    labels  <- paste(isParty,labels,sep="")

    missPrices <- all(is.na(object@pricePre))

    if(missPrices){
      outPre=calcShares(object,preMerger=TRUE)
      outPost=calcShares(object,preMerger=FALSE)
    }
    else{
      outPre=calcQuantities(object,preMerger=TRUE)
      outPost=calcQuantities(object,preMerger=FALSE)
    }

    prices<-quantPre<-quantPost<-prod<-NULL

    plotThis <- function(price,idx,preMerger){
      thisObj=object
      if(preMerger){thisObj@pricePre[idx]=price}
      else{thisObj@pricePost[idx]=price}

      if(!missPrices){
        return(calcQuantities(thisObj,preMerger=preMerger)[idx])
      }
      else{return(calcShares(thisObj,preMerger=preMerger)[idx])}
    }

    for(i in 1:nprods){
      thesePrices=seq((1-scale)*min(mcPre[i],mcPost[i],na.rm=TRUE),(1+scale)*max(pricePre[i],pricePost[i],na.rm=TRUE),length.out=100)
      quantPre=c(quantPre,sapply(thesePrices,plotThis,idx=i,preMerger=TRUE))
      quantPost=c(quantPost,sapply(thesePrices,plotThis,idx=i,preMerger=FALSE))
      prices=c(prices,thesePrices)
      prod=c(prod,rep(labels[i],length(thesePrices)))
    }

    resultPre=data.frame(output=quantPre,price=prices,prod=prod,Demand="pre-merger")
    resultPost=data.frame(output=quantPost,price=prices,prod=prod,Demand="post-merger")
    result=rbind(resultPre,resultPost)
    result=result[result$output>0,]

    equilibria=data.frame(output=c(outPre,
                                   outPost),
                          price=c(pricePre,pricePost),
                          mc=c(mcPre,mcPost),
                          prod=labels,
                          Demand=rep(c("pre-merger","post-merger"),each=nprods))
    equilibria$Cost=equilibria$Demand


    thisPlot=ggplot2::ggplot(result,(ggplot2::aes_string(x='output',y='price',color='Demand',group='Demand'))) + ggplot2::geom_line() + ggplot2::theme_bw() + ggplot2::theme(legend.position="bottom", legend.direction="horizontal",legend.title=ggplot2::element_blank())
    thisPlot=thisPlot + ggplot2::facet_wrap(~prod,scales="free_x")

    thisPlot=thisPlot + ggplot2::geom_vline(ggplot2::aes_string(xintercept = "output",group="Demand",colour="Demand"),linetype=3,equilibria[,c("output","Demand","prod")] )
    thisPlot=thisPlot + ggplot2::geom_hline(ggplot2::aes_string(yintercept = "price",group="Demand",colour="Demand"),linetype=3,equilibria[,c("price","Demand","prod")] )
    thisPlot=thisPlot + ggplot2::geom_point(ggplot2::aes_string(y="price",x="output",color="Demand",group="Demand"),equilibria)

    thisPlot=thisPlot + ggplot2::geom_hline(ggplot2::aes_string(yintercept = "mc",group="Cost",color="Cost"),data=equilibria[,c("mc","Cost","prod")],show_guide=TRUE)

    #if(!isTRUE(all.equal(mcPre,mcPost,check.names=FALSE))){
    #  thisPlot=thisPlot + geom_hline(aes(yintercept = mc), color="orange",data=data.frame(mc=mcPost[mcPost!=mcPre],prod=labels[mcPost!=mcPre]),show_guide=TRUE)

    #}


    return(thisPlot)
  }
)