From: "Kandem, Vamshi Krishna" <Vamshi-Krishna.Kandem@...>
Date: 2007-03-30T18:59:58+09:00
Subject: Re: Ruby math.pow equivalent



Hi john,

This the answer.

@principal*@rate/(1-(1/(1+@rate))**@payments )

Thanks
VamshiK


-----Original Message-----
From: list-bounce@example.com [mailto:list-bounce@example.com] On Behalf
Of John Butler
Sent: Friday, March 30, 2007 2:52 PM
To: ruby-talk ML
Subject: Re: Ruby math.pow equivalent

Drew Olson wrote:
> John Butler wrote:
>> Hi,
>> 
>> I am trying to calculate a monthly payment for a loan in Ruby.  Does
>> anyone know what the equivalent for math.pow in Java is for Ruby?
>> 
>> @monthlypayment =
@principal*@rate/(1-Math.pow(1/(1+@rate),@payments))
>> 
>> Ive searched everywhere and cant seem to find anything.
>> 
>> thanks
>> 
>> Johnny B
> 
> I think this is what you're looking for:
> 
> irb(main):001:0> 2 ** 1
> => 2
> irb(main):002:0> 2 ** 2
> => 4
> irb(main):003:0> 2 ** 3
> => 8
> irb(main):004:0> 2 ** 4
> => 16



Yes this is what i am looking for. How do i then use it to calculate 
amonthly payment, i have tried quite a few things but cant get the 
syntax right: @monthlypayment = 
@principal*@rate/(1-**(1/(1+@rate),@payments))


So for the example below:

Suppose you finance your car with a loan of $12000 at a yearly interest 
rate of 11% for four years, and make equal payments monthly. How much 
will your payments have to be? Here the parameters are principal P = 
$12000, interest rate i = 0.11, number of years n = 4, and number of 
periods per year q = 12. Then the monthly car payment M is given by

    M = Pi/[q(1-[1+(i/q)]-nq)],
      = ($12000)(0.11)/[(12)(1-[1+(0.11/12)]-(4)(12))],
      = $110/(1-1.009166666...-48),
      = $310.15.


Anyone done this before?


-- 
Posted via http://www.ruby-forum.com/.

This email is confidential. If you are not the addressee tell the sender immediately and destroy this email
without using, sending or storing it. Emails are not secure and may suffer errors, viruses, delay,
interception and amendment. Standard Chartered PLC and subsidiaries ("SCGroup") do not accept liability for
damage caused by this email and may monitor email traffic.