Question

I need help with Problem 4 from PS4. I cannot figure out what my if statement should be in the binary search. If I do the problem manually, knowing the answer it's easy as I know when to assign the guess from low to high. I get the correct answers for parts 1-3, so I know that's not the issue.

Answer 1

def findMaxExpenses(salary, save, preRetireGrowthRates, postRetireGrowthRates, epsilon):

low = 0
est_high = nestEggVariable(salary, save, preRetireGrowthRates)
high = est_high[-1] # amount of money at start of retirement


guess = (low + high)/2.0

retirement_list = postRetirement(high, postRetireGrowthRates, guess)

money_end_retirement = retirement_list[-1]

print money_end_retirement

while abs(money_end_retirement) > epsilon:

print guess # printing the expenses guess each iteration

if ?????:

high = guess

guess = (low + high) / 2.0

retirement_list = postRetirement(high, postRetireGrowthRates, guess)

money_end_retirement = retirement_list[-1]


else:

low = guess

guess = (low + high) /2.0

retirement_list = postRetirement(high, postRetireGrowthRates, guess)

money_end_retirement = retirement_list[-1]


print "final estimate is ", guess



Am I on the right track? Any help is greatly appreciated! :)

Answer 2

Yes, you're on the right track. Figure out how your guess affects the money_end_retirement, and you will know what to check for in your IF statement.

Answer 3

Thanks Aslander!! Turns out my original assumption of if money_end_retirement < 0: was correct, but I had the wrong value for my savings in postRetirement function. It should've been the money at the start of retirement. It threw me off!