ps4.py

# Problem Set 4
# Name: Vaboro
# Collaborators: None
# Time: N/A

#
# Problem 1
#

def nestEggFixed(salary, save, growthRate, years):
    """
    - salary: the amount of money you make each year.
    - save: the percent of your salary to save in the investment account each
      year (an integer between 0 and 100).
    - growthRate: the annual percent increase in your investment account (an
      integer between 0 and 100).
    - years: the number of years to work.
    - return: a list whose values are the size of your retirement account at
      the end of each year.
    """
    # TODO: Your code here.

    retirement_account = [salary * save * 0.01,]

    for i in range(years-1):

        retirement_account.append(retirement_account[i] * (1 + growthRate * 0.01) + salary * save * 0.01)

    return retirement_account



def testNestEggFixed():
    salary     = 10000
    save       = 10
    growthRate = 15
    years      = 5
    savingsRecord = nestEggFixed(salary, save, growthRate, years)
    print savingsRecord
    # Output should have values close to:
    # [1000.0, 2150.0, 3472.5, 4993.375, 6742.3812499999995]

    # TODO: Add more test cases here.

    salary     = 20000
    save       = 10
    grothRate  = 15
    years      = 5
    savingsRecord = nestEggFixed(salary, save, growthRate, years)
    print savingsRecord

    salary     = 10000
    save       = 10
    grothRate  = 15
    years      = 10
    savingsRecord = nestEggFixed(salary, save, growthRate, years)
    print savingsRecord


#
# Problem 2
#

def nestEggVariable(salary, save, growthRates):
    # TODO: Your code here.
    """
    - salary: the amount of money you make each year.
    - save: the percent of your salary to save in the investment account each
      year (an integer between 0 and 100).
    - growthRates: a list of the annual percent increases in your investment
      account (integers between 0 and 100).
    - return: a list of your retirement account value at the end of each year.
    """

    retirement_account = [salary * save * 0.01,]

    for i in range(len(growthRates)-1):

        retirement_account.append(retirement_account[i] * (1 + growthRates[i+1] * 0.01) + salary * save * 0.01)

    return retirement_account

def testNestEggVariable():
    salary      = 10000
    save        = 10
    growthRates = [3, 4, 5, 0, 3]
    savingsRecord = nestEggVariable(salary, save, growthRates)
    print savingsRecord
    # Output should have values close to:
    # [1000.0, 2040.0, 3142.0, 4142.0, 5266.2600000000002]

    # TODO: Add more test cases here.

    salary      = 10000
    save        = 10
    growthRates = [3, 4, 5, 0, 3, 5, 2, 7, 9]
    savingsRecord = nestEggVariable(salary, save, growthRates)
    print savingsRecord

    salary      = 20000
    save        = 5
    growthRates = [3, 4, 5, 0, 3, 2, 3, 1, 5, 7]
    savingsRecord = nestEggVariable(salary, save, growthRates)
    print savingsRecord

#
# Problem 3
#

def postRetirement(savings, growthRates, expenses):
    """
    - savings: the initial amount of money in your savings account.
    - growthRate: a list of the annual percent increases in your investment
      account (an integer between 0 and 100).
    - expenses: the amount of money you plan to spend each year during
      retirement.
    - return: a list of your retirement account value at the end of each year.
    """
    # TODO: Your code here.

    fund_size = [savings * (1 + 0.01 * growthRates[0]) - expenses,]

    for i in range(len(growthRates)-1):

        fund_size.append(fund_size[i] * (1 + 0.01 * growthRates[i+1]) - expenses)

    return fund_size

def testPostRetirement():
    savings     = 100000
    growthRates = [10, 5, 0, 5, 1]
    expenses    = 30000
    savingsRecord = postRetirement(savings, growthRates, expenses)
    print savingsRecord
    # Output should have values close to:
    # [80000.000000000015, 54000.000000000015, 24000.000000000015,
    # -4799.9999999999854, -34847.999999999985]

    # TODO: Add more test cases here.

    savings     = 200000
    growthRates = [10, 5, 0, 5, 1,0,3,2]
    expenses    = 10000
    savingsRecord = postRetirement(savings, growthRates, expenses)
    print savingsRecord

    savings     = 80000
    growthRates = [10, 5, 0, 5, 1,4,6,8]
    expenses    = 20000
    savingsRecord = postRetirement(savings, growthRates, expenses)
    print savingsRecord

#
# Problem 4
#

def findMaxExpenses(salary, save, preRetireGrowthRates, postRetireGrowthRates,
                    epsilon):
    """
    - salary: the amount of money you make each year.
    - save: the percent of your salary to save in the investment account each
      year (an integer between 0 and 100).
    - preRetireGrowthRates: a list of annual growth percentages on investments
      while you are still working.
    - postRetireGrowthRates: a list of annual growth percentages on investments
      while you are retired.
    - epsilon: an upper bound on the absolute value of the amount remaining in
      the investment fund at the end of retirement.
    """
    # TODO: Your code here.

    retirement_account = nestEggVariable(salary,save,preRetireGrowthRates)
    retirement_fund = retirement_account[len(retirement_account)-1]
    expenses_low = 0
    expenses_high = retirement_fund
    expenses = (expenses_high + expenses_low) / 2
    savings_account = postRetirement(retirement_fund, postRetireGrowthRates, expenses)
    savings_left = savings_account[len(savings_account)-1]

    while abs(savings_left) > epsilon:
        print "Current expenses estimate =", expenses, "Savings left =", savings_left,
        if savings_left < 0:
            expenses_high = expenses
            print "Previous expenses low =", expenses_low, "New expenses high =", expenses_high
        else:
            expenses_low = expenses
            print "New expenses low =", expenses_low, "Previous expenses high =", expenses_high
        expenses = (expenses_high + expenses_low) / 2
        savings_account = postRetirement(retirement_fund, postRetireGrowthRates, expenses)
        savings_left = savings_account[len(savings_account)-1]

    return expenses


def testFindMaxExpenses():
    salary                = 10000
    save                  = 10
    preRetireGrowthRates  = [3, 4, 5, 0, 3]
    postRetireGrowthRates = [10, 5, 0, 5, 1]
    epsilon               = 0.01
    expenses = findMaxExpenses(salary, save, preRetireGrowthRates,
                               postRetireGrowthRates, epsilon)
    print expenses
    # Output should have a value close to:
    # 1229.95548986

    # TODO: Add more test cases here.

    salary                = 20000
    save                  = 15
    preRetireGrowthRates  = [3, 4, 5, 0, 3, 4, 8, 1]
    postRetireGrowthRates = [10, 5, 0, 5, 1]
    epsilon               = 0.01
    expenses = findMaxExpenses(salary, save, preRetireGrowthRates,
                               postRetireGrowthRates, epsilon)
    print expenses

    salary                = 50000
    save                  = 10
    preRetireGrowthRates  = [3, 4, 5, 0, 3, 4, 6, 7, 9, 1, 2]
    postRetireGrowthRates = [10, 5, 0, 5, 1]
    epsilon               = 0.01
    expenses = findMaxExpenses(salary, save, preRetireGrowthRates,
                               postRetireGrowthRates, epsilon)
    print expenses