Question

PS4 again.. Has anyone tried solving Q4 with the Newton-Raphson method? I'm guessing it's not possible or severely complicated given that interest rates vary every iteration?

Answer 1

Interesting question. Theoretically savings would be x, expenses would be a constant k. Growth rate varies with year. From year 2 onwards you potentially have a quadratic equation in x.

I tried giving it a shot but the variable growth rate complicated matters considerably for me.

Answer 2

http://codepad.org/7DFWEOW0

the function we are solving for looks pretty linear - it only takes one iteration to find 'the root'

the variable growth rates constant and the initial savings are constant
that is the rates in the list may be different from year to year but that list of rates stays the same while expenses are changed
- expenses are the dependent variable
- the list of growth rates is a constant

Answer 3

bwCA: Thank you. There are still some parts that I'm not familiar (eg lambda) with but the answers do match. I'll touch base with it once I've have a better grasp of Python.

Answer 4

lambda is a quick and dirty way of making a function