// Advanvced Part 3 about really dumb investing strategy+
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//=======================================================+
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+
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//two test portfolios+
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+
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val blchip_portfolio = List("GOOG", "AAPL", "MSFT", "IBM", "FB", "YHOO", "AMZN", "BIDU")+
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val rstate_portfolio = List("PLD", "PSA", "AMT", "AIV", "AVB", "BXP", "CBG", "CCI", +
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                            "DLR", "EQIX", "EQR", "ESS", "EXR", "FRT", "GGP", "HCP") +
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+
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// (1) The function below should obtain the first trading price+
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// for a stock symbol by using the query+
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//+
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//    http://ichart.yahoo.com/table.csv?s=<<symbol>>&a=0&b=1&c=<<year>>&d=1&e=1&f=<<year>> +
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// +
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// and extracting the first January Adjusted Close price in a year.+
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+
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import io.Source+
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import scala.util._+
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+
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def get_yahoo_page(url: String): Option[List[String]] = {+
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  Try(Some(Source.fromURL(url)("ISO-8859-1").getLines.toList)).+
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    getOrElse { None }+
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}+
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+
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def get_first_price(symbol: String, year: Int): Option[Double] = {+
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  //println(s"download..${symbol} at ${year}")+
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  val year_string = year.toString+
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  val date_string = s"&a=0&b=1&c=${year_string}&d=1&e=1&f=${year_string}"+
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  val url = """http://ichart.yahoo.com/table.csv?s=""" + symbol + date_string+
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  val data = get_yahoo_page(url)+
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  data.map(_.last.split(",").toList(6).toDouble)+
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}+
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+
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+
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// Complete the function below that obtains all first prices+
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// for the stock symbols from a portfolio for the given+
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// range of years+
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+
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def get_prices(portfolio: List[String], years: Range): List[List[Option[Double]]] = +
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  for (year <- years.toList) yield+
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    for (symbol <- portfolio) yield get_first_price(symbol, year)+
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+
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+
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// test case+
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//val p = get_prices(List("GOOG", "AAPL"), 2010 to 2012)+
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+
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+
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// (2) The first function below calculates the change factor (delta) between+
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// a price in year n and a price in year n+1. The second function calculates+
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// all change factors for all prices (from a portfolio).+
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+
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def get_delta(price_old: Option[Double], price_new: Option[Double]): Option[Double] = {+
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  (price_old, price_new) match {+
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    case (Some(x), Some(y)) => Some((y - x) / x)+
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    case _ => None+
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  }+
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}+
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+
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def get_deltas(data: List[List[Option[Double]]]):  List[List[Option[Double]]] =+
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  for (i <- (0 until (data.length - 1)).toList) yield +
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    for (j <- (0 until (data(0).length)).toList) yield get_delta(data(i)(j), data(i + 1)(j))+
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+
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+
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// test case using the prices calculated above+
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//val d = get_deltas(p)+
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+
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+
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// (3) Write a function that given change factors, a starting balance and a year+
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// calculates the yearly yield, i.e. new balanace, according to our dump investment +
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// strategy. Another function calculates given the same data calculates the+
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// compound yield up to a given year. Finally a function combines all +
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// calculations by taking a portfolio, a range of years and a start balance+
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// as arguments.+
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+
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+
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def yearly_yield(data: List[List[Option[Double]]], balance: Long, year: Int): Long = {+
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  val somes = data(year).flatten+
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  val somes_length = somes.length+
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  if (somes_length == 0) balance+
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  else {+
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    val portion: Double = balance / somes_length+
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    balance + (for (x <- somes) yield (x * portion)).sum.toLong+
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  }+
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}+
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+
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//test case+
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//yearly_yield(d, 100, 0)+
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+
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def compound_yield(data: List[List[Option[Double]]], balance: Long, year: Int): Long = {+
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  if (year >= data.length) balance else {+
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    val new_balance = yearly_yield(data, balance, year)+
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    compound_yield(data, new_balance, year + 1)+
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  }+
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}+
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+
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def investment(portfolio: List[String], years: Range, start_balance: Long): Long = {+
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  compound_yield(get_deltas(get_prices(portfolio, years)), start_balance, 0)+
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}+
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+
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+
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//test cases for the two portfolios given above+
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+
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println("Real data: " + investment(rstate_portfolio, 1978 to 2016, 100))+
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println("Blue data: " + investment(blchip_portfolio, 1978 to 2016, 100))+
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+
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