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From: J on 28 Jun 2010 13:42
Greetings:

I am attempting to create a vector of compound returns with a fixed starting principal amount and variable returns per period. For example:

I had capital = $10,000 at time 0.

My return, r, at the following periods:

r1 = 1.2%
r2 = 2.3%
r3 = -1.2%
…

My $10,000 compounds at the rates above per period.

So:

x1 = capital * (1 + r1)
x2 = x1 * (1 + r2)
x3 = x2 * (1 + r3)
....

My main issue is probably simple for those with experience in MATLAB. I'm having troube recursively calling the x in the above example. For example:

r is a vector of returns
capital is the initial capital ($10,000)

I modified compint (http://www.mathworks.com/matlabcentral/newsreader/view_thread/259630#676655) to return a 1-period return:

%%%

function a = compint(p, r)
%p=starting balance, r=return %

a = (p) * (1 + r);

%%%

I try to run the following code:

capital = compint(capital, r(:,1));

which simply multiplies the return at period t against the original starting capital. I would like it to of course recursively (or otherwise) multiply the next return against the previous capital + return.

I'm very new to MATLAB and hoping there is a built in function or someone has accomplished this task.
From: J on 28 Jun 2010 17:44
Very easy:

series = [cumprod(r) * capital];



"J " <remove.this.strimp101(a)gmail.com> wrote in message <i0amth$77$1(a)fred.mathworks.com>...
> Greetings:
>
> I am attempting to create a vector of compound returns with a fixed starting principal amount and variable returns per period. For example:
>
> I had capital = $10,000 at time 0.
>
> My return, r, at the following periods:
>
> r1 = 1.2%
> r2 = 2.3%
> r3 = -1.2%
> &#8230;
>
> My $10,000 compounds at the rates above per period.
>
> So:
>
> x1 = capital * (1 + r1)
> x2 = x1 * (1 + r2)
> x3 = x2 * (1 + r3)
> ...
>
> My main issue is probably simple for those with experience in MATLAB. I'm having troube recursively calling the x in the above example. For example:
>
> r is a vector of returns
> capital is the initial capital ($10,000)
>
> I modified compint (http://www.mathworks.com/matlabcentral/newsreader/view_thread/259630#676655) to return a 1-period return:
>
> %%%
>
> function a = compint(p, r)
> %p=starting balance, r=return %
>
> a = (p) * (1 + r);
>
> %%%
>
> I try to run the following code:
>
> capital = compint(capital, r(:,1));
>
> which simply multiplies the return at period t against the original starting capital. I would like it to of course recursively (or otherwise) multiply the next return against the previous capital + return.
>
> I'm very new to MATLAB and hoping there is a built in function or someone has accomplished this task.
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