Bisection Loop

[Anon]

I am working on a script to find the interest rate of a loan, given p, pmt, and n.

The script works but I used an incremental loop to solve for i. It has been suggested to me that a bisection loop would yield a much faster result as well as being very accurate. Problem is I am not sure how to what is involved. Can anyone explain it to me in terms of php.

Thanks

Jeff

[Anon]

(left off the last part of the message)... the brief explination I got was that you have a high and a low value, calculate an average and than iterate.

Jeff

[majik-sheff]

I assume this is what you mean by those values:

p = principal
pmt = payment amount
n = number of payments

If that's the case, this should give you your interest rate:

i = (pmt * n - p) / p

[Anon]

Thank you for your help. Unfortunately there is no direct solution for the solving of i (rate). You have to start with a guess and than do iteration to come up with the answer.

Jeff

[majik-sheff]

Well then post your code and maybe I or someone else can optimize it.