iap purchase update

gistfile1.cs

public UserIapModel Calculate(double? currentTotalIap,
			double? currentElapsedHours,
			double? currentPlayedTurns,
			double newIap,
			double newElapsedHours,
			double newPlayedTurns)
{
    // default setting for new users: spending $0.01 in every 24 hours or 10 turns
    double totalIap = currentTotalIap ?? 0.01;
    double totalElapsedHours = currentElapsedHours ?? 24;
    double totalPlayedTurns = currentPlayedTurns ?? 10;

    // normalized hours should be between 1 hour and 2160 hours (90 days)
    var normalizedHours = Math.Max(1., Math.Min(2160, newElapsedHours));
    // normalized turns should be between 3 turns and 5000 turns)
    var normalizedTurns = Math.Max(3., Math.Min(5000, newPlayedTurns));

    // this is the database data access object
    var userIapModel = new UserIapModel();
    userIapModel.totalIap = totalIap + newIap;
    userIapModel.totalElaspedHours = totalElaspedHours + normalizedHours;
    userIapModel.totalPlayedTurns = totalPlayedTurns + normalizedTurns;

    // metric 1: daily iap
    var meanHourlyIap = userIapModel.totalIap/userIapModel.totalElapsedHours;
    var stdHourlyIap = Math.Sqrt(userIapModel.totalIap/(userIapModel.totalElaspedHours*userIapModel.totalElaspedHours));
    var stdDailyIap = stdHourlyIap*24.0;

    userIapModel.meanDailyIap = userIapModel.meanHourlyIap*24.0;
    userIapModel.upperBoundDailyIap = userIapModel.meanDailyIap + 2*stdDailyIap;
    userIapModel.lowerBoundDailyIap = Math.Max(0.0, userIapModel.meanDailyIap - 2*stdDailyIap);

    // metric 2: iap per 100 turns
    var meanIapPerTurn = userIapModel.totalIap/userIapModel.totalPlayedTurns;
    var stdIapPerTurn = Math.Sqrt(userIapModel.totalIap/(userIapModel.totalPlayedTurns*userIapModel.totalPlayedTurns));
    var stdIapPerHundredTurns = stdIapPerTurn*100.0;
    userIapModel.meanIapPerHundredTurns = meanIapPerTurn*100.0;
    userIapModel.upperBoundIapPerHundredTurns = userIapModel.meanIapPerHundredTurns + 2*stdIapPerHundredTurns;
    userIapModel.lowerBoundIapPerHundredTurns = Math.Max(0.0, userIapModel.meanIapPerHundredTurns - 2*stdIapPerHundredTurns);
	
    return userIapModel;
}