Forum: Ruby Ruby math.pow equivalent

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John B. (Guest)
on 2007-03-30 00:43
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
Brian C. (Guest)
on 2007-03-30 01:02
(Received via mailing list)
On Fri, Mar 30, 2007 at 05:43:38AM +0900, John B. wrote:
> 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.

http://www.rubycentral.com/book/ref_c_float.html#F...

Look for 'exponentiation'
Harry H. (Guest)
on 2007-03-30 01:07
(Received via mailing list)
On 3/30/07, John B. <removed_email_address@domain.invalid> wrote:
> Does
> anyone know what the equivalent for math.pow in Java is for Ruby?
>
> @monthlypayment = @principal*@rate/(1-Math.pow(1/(1+@rate),@payments))
>
>

Is this what you are looking for?

p 4 ** 3

Harry

--

http://www.kakueki.com/ruby/list.html
Japanese Ruby List Subjects in English
Drew O. (Guest)
on 2007-03-30 01:08
John B. 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
John B. (Guest)
on 2007-03-30 13:21
Drew O. wrote:
> John B. 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?
Stefano C. (Guest)
on 2007-03-30 13:53
(Received via mailing list)
Alle venerdì 30 marzo 2007, John B. ha scritto:
> >>
> > irb(main):003:0> 2 ** 3
> So for the example below:
>       = $310.15.
>
>
> Anyone done this before?


** is an operator, just like + or *; it's used this way: base**exponent.
In
your case, you should write:
@principal*@rate/(1-1/(1+@rate)**@payments)

I hope this helps

Stefano
John B. (Guest)
on 2007-03-30 16:53
Yes, thanks.
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