R/play_game_orig_loop.R

In ndavis4904/MontyHall: Monty Hall Problem and its Variants

#' The original Monty Hall game run N times
#' 
#' @param N Number of loops of the play_game() function.
#' @param ... further arguments passed to or from other methods.
#' 
#' @return The number of goats added to the number of cars makes the total number of doors to choose from.
#' N is then how many simulations it will run. N*2 is the number of datapoints in the dataframe.
#' @examples
#' ## Monty Hall Problem with 2 goats, 1 car, and run 100 times.
#' play_game(N = 100)
#' 
#' ## Monty Hall run the standard 10,000 times.
#' play_game()
#' 
#' @export
play_game_orig_loop <- function(N = 10000) {
  play_game_orig <- function( )
  {
    create_game <- function( )
    {
      a.game <- sample( x=c("goat","goat","car"), size=3, replace=F )
      return( a.game )
    } 
    
    select_door <- function( )
    {
      doors <- c(1,2,3) 
      a.pick <- sample( doors, size=1 )
      return( a.pick )  # number between 1 and 3
    }
    
    open_goat_door <- function( game, a.pick )
    {
      doors <- c(1,2,3)
      # if contestant selected car,
      # randomly select one of two goats 
      if( game[ a.pick ] == "car" )
      { 
        goat.doors <- doors[ game != "car" ] 
        opened.door <- sample( goat.doors, size=1 )
      }
      if( game[ a.pick ] == "goat" )
      { 
        opened.door <- doors[ game != "car" & doors != a.pick ] 
      }
      return( opened.door ) # number between 1 and 3
    }
    
    change_door <- function( stay=T, opened.door, a.pick )
    {
      doors <- c(1,2,3) 
      
      if( stay )
      {
        final.pick <- a.pick
      }
      if( ! stay )
      {
        final.pick <- doors[ doors != opened.door & doors != a.pick ] 
      }
      
      return( final.pick )  # number between 1 and 3
    }
    
    determine_winner <- function( final.pick, game )
    {
      if( game[ final.pick ] == "car" )
      {
        return( "WIN" )
      }
      if( game[ final.pick ] == "goat" )
      {
        return( "LOSE" )
      }
    }
    
    new.game <- create_game()
    first.pick <- select_door()
    opened.door <- open_goat_door( new.game, first.pick )
    final.pick.stay <- change_door( stay=T, opened.door, first.pick )
    final.pick.switch <- change_door( stay=F, opened.door, first.pick )
    outcome.stay <- determine_winner( final.pick.stay, new.game  )
    outcome.switch <- determine_winner( final.pick.switch, new.game )
    
    strategy <- c("Stay","Switch")
    outcome <- c(outcome.stay,outcome.switch)
    game.results <- data.frame( strategy, outcome,
                                stringsAsFactors=F )
    return( game.results )
  }
  
  results.df <- NULL
  for(i in 1:N) {
    game.outcome <- play_game_orig()
    results.df <- rbind(results.df, game.outcome)
  }
  return(results.df)
}