Velocity Reviews > Exponentiation in a Formula

# Exponentiation in a Formula

grahamhow424@hotmail.com
Guest
Posts: n/a

 12-21-2006
Hi

I am trying to figure out how to duplicate a, financial, calculation
that uses the caret, Exponentiation.

Here's the formula...

A = 0.0755
B = 34
C = 50000
D = 22448

result = ((C-D)*A/12)/(1-(1+A/12)^(-B))+D*A/12

It calculates loan repayments based on interest rate (A), number of
payments (B), total loan amount (C) and a residual amount (D).

This calculation will work when the caret (Exponentiation) is used,
however this is not available in Javascript. So, to get this formula to
work in Javascript some other method needs to be used.

I have found examples of how to do Exponentiation, like this:

/************************************************** *********/

function powmod(base,exp,modulus)
{
var accum=1, i=0, basepow2=base;
while ((exp>>i)>0)
{
if(((exp>>i) & 1) == 1){accum = (accum*basepow2) % modulus;};
basepow2 = (basepow2*basepow2) % modulus;
i++;
};
return accum;
}

/************************************************** *********/

This function comes from here
http://www.math.umbc.edu/~campbell/N...pt.html#PowMod (some handy stuff
there) but I can't replicate the calculation I have posted using a
function like that.

Anyone know how to do this?

Thanks!

-Lost
Guest
Posts: n/a

 12-22-2006
<(E-Mail Removed)> wrote in message
news:(E-Mail Removed) ps.com...
> Hi
>
> I am trying to figure out how to duplicate a, financial, calculation
> that uses the caret, Exponentiation.
>
> Here's the formula...
>
> A = 0.0755
> B = 34
> C = 50000
> D = 22448
>
> result = ((C-D)*A/12)/(1-(1+A/12)^(-B))+D*A/12

result = ((C-D)*A/12)/(1-Math.pow((1+A/12),(-B)))+D*A/12;

-Lost

grahamhow424@hotmail.com
Guest
Posts: n/a

 12-22-2006
Hi David

Thanks, I got it now.

The formula I posted previously could translate in JS as...

var A1 = 0.0755;
var B1 = 34;
var C1 = 50000;
var D1 = 22448;

alert(((C1 - D1) * A1 / 12) / (1 - Math.pow((1 + A1 / 12), -B1)) + (D1
* A1 / 12));

Thanks again!

David Golightly wrote:
> The caret operator (^) is the bitwise XOR operator in JavaScript. Use
> Math.pow for exponents:
>
> Math.pow(2,3)
> => 8

-Lost
Guest
Posts: n/a

 12-22-2006
<(E-Mail Removed)> wrote in message
news:(E-Mail Removed) ps.com...
> Hi David
>
> Thanks, I got it now.
>
> The formula I posted previously could translate in JS as...
>
> var A1 = 0.0755;
> var B1 = 34;
> var C1 = 50000;
> var D1 = 22448;
>
> alert(((C1 - D1) * A1 / 12) / (1 - Math.pow((1 + A1 / 12), -B1)) + (D1
> * A1 / 12));

result = ((C-D)*A/12)/(1-Math.pow((1+A/12),(-B)))+D*A/12;

That is the exact same thing I wrote (a few minutes before you posted again).

-Lost

grahamhow424@hotmail.com
Guest
Posts: n/a

 12-22-2006
Ahhhh -Lost

You nailed it. Unfortunately I sorted it out while you were posting,
wish you posted about 3 mins earlier!

Anyway, thanks a lot, appreciate your input.

-Lost wrote:
> <(E-Mail Removed)> wrote in message
> news:(E-Mail Removed) ps.com...
> > Hi David
> >
> > Thanks, I got it now.
> >
> > The formula I posted previously could translate in JS as...
> >
> > var A1 = 0.0755;
> > var B1 = 34;
> > var C1 = 50000;
> > var D1 = 22448;
> >
> > alert(((C1 - D1) * A1 / 12) / (1 - Math.pow((1 + A1 / 12), -B1)) + (D1
> > * A1 / 12));

>
> result = ((C-D)*A/12)/(1-Math.pow((1+A/12),(-B)))+D*A/12;
>
> That is the exact same thing I wrote (a few minutes before you posted again).
>
> -Lost

Dr J R Stockton
Guest
Posts: n/a

 12-22-2006
In comp.lang.javascript message
<(E-Mail Removed) om>, Thu, 21 Dec 2006
15:24:20, http://www.velocityreviews.com/forums/(E-Mail Removed) wrote:
>
>I am trying to figure out how to duplicate a, financial, calculation
>that uses the caret, Exponentiation.

In Javascript, X = Base^Expo is actually bitwise exclusive-or, and
X = Math.pow(Base, Expo) exponentiates. Read any relevant book.

It's a good idea to read the newsgroup and its FAQ. See below.

--
(c) John Stockton, Surrey, UK. ?@merlyn.demon.co.uk Turnpike v6.05 IE 6
news:comp.lang.javascript FAQ <URL:http://www.jibbering.com/faq/index.html>.
<URL:http://www.merlyn.demon.co.uk/js-index.htm> jscr maths, dates, sources.

-Lost
Guest
Posts: n/a

 12-22-2006
<(E-Mail Removed)> wrote in message
news:(E-Mail Removed) ups.com...

> Ahhhh -Lost
>
> You nailed it. Unfortunately I sorted it out while you were posting,
> wish you posted about 3 mins earlier!
>
> Anyway, thanks a lot, appreciate your input.

Heh. No problem!

-Lost