Question

Hi,
The solution to #2 for Problem set # 1 seems incomplete. I could be wrong, but it doesn't test for if the monthly payment needs to be reduced. Also I'm getting vastly different numbers from the answer key using the test case. I tested it in Excel and my program matches that though.

Can anyone look at my code? Thanks a lot.

Answer 1

It's the uncommented portion of the attached file. I know I should clean my code up a bit, seems a bit redundant...but the logic is:

I'm checking for the initial guess being larger vs smaller (bisection guessing).

If it is too small, I go to the first chunk of code. If it is too large I go to the second.

Note, I did make sure to add interest PRIOR to any deductions as the professor specified. Excel checks out as well. I will attach.

Answer 2

Attached Excel with the 1200 Balance, .18 example

Answer 3

I also noticed he didn't make it pay in increments of 10 in his attached answer sheet, or check for a payment that is too large.

Answer 4

Attached problem set for ease of use.

Answer 5

I'm not on that problem yet. I am having problems with a syntax error in the second one. Let me get there and then I will be able to give you a more informed guess.

Answer 6

Were you able to get the first portion of code to work properly before diving into the bisection search? I am getting ready to transform my working code into the faster bisection method today.

Answer 7

In fact, you dont use bisection search in your answer. You use upper and lower bound to make an educated guess at the beginning "MinPay = round((High + Low)/2.0, -1)" but after that you keep adding or substracting 10$ if the initial guess is too high/too low.

Using bisection search means you make a guess using predetermined bounds, and you modify these upper/lower bound once you calculated the balance with the guess.

If the guess is too high ( = balance is negative), you set the upper bound to be the current actual guess. Vice versa if the current guess is too low ( = balance is still positive) it becomes the lower bound.

Then, the next time your loop is executed, the guess should be based on these new upper/lower bounds. It will allow you to progressively pinpoint a reliable guess.

Now you just have to deal with guess precision : when do you think the guess is precise enough to be kept.

Answer 8

strategically placed print statements are a great way to 'debug' your code.
http://dpaste.com/1324113/

the while loops that run thru 12 months of payments - you probably shouldn't round at each iteration.

you could greatly simplify your code: if you just start with a minpay of $10 then you won't have to worry about decreasing it - this change would get rid of almost half your code and possibly make it easier to read and debug.

your solution is definitely not working