Gompertz Function among Any Other

[Dicky]

Hello everyone, nice to meet you.

I am new to statistics world and the site of zunzun.com but i see a
great deal of it.
It help me on learning about many function, regression, and other
thing.

But on my learning, i got stuck on something.
When I see a new function I can use it on zunzun, but I dont
understand it.

For example, Gompertz C function, I understand about how to get a, b,
c in zunzun,
But, i dont understand how does the program calculate it? what is the
formula to get a, b, and c?

I dont have problem with normal function such as Linear Regression,
Logaritmic Regression, after all there are many reference in other
site. But Gompertz, lol, well, 2 days searching and still no clues
about this one.

Does anyone, especially all who create zunzun have some reference
about this formula (among any other).
If any of you have one. It would really help me.

Thank you, and once again, hello to you.
please welcome me in this statistics world.


Dicky W,
Sharing Vision.

[zunzun.com]

There are two basic types of curve fitting: linear and non-linear.  For non-linear, there are many methods.  For non-linear regression, ZunZun.com uses a genetic algorithm to find a starting point, then uses Levenberg-Marquardt followed by Downhill Simplex.  Using these non-linear methods means the coefficients cannot be directly expressed using a formula.  This is a large area of study.

 

The fitting source code for the web site is at http://code.google.com/p/pyeq2/downloads/list

 

     James

[Dicky]

We are currently using zunzun algorithm to determine regression
function in our application.
But we really need some ground theory to goes along the function.

You said "Uses a genetic algorithm, levenberg-marquardt, downhill
simplex"
Are those sentence only applied to gompertz algorithm only, or can be
applied to another algorithm.
If those sentence only applied to gompertz algorithm only,

I really hope you could help me on describing some function:
- Exponential
- Standard Power
I have check all those function and the result is different with excel
and standard function and all those function is not
fit with zunzun function

Thank you very much,

Dicky W

On Mar 8, 9:19 pm, "zunzun.com" <zunzun....@gmail.com> wrote:
> There are two basic types of curve fitting: linear and non-linear.  For
> non-linear, there are many methods.  For non-linear regression, ZunZun.com
> uses a genetic algorithm to find a starting point, then uses
> Levenberg-Marquardt followed by Downhill Simplex.  Using these non-linear
> methods means the coefficients cannot be directly expressed using a
> formula.  This is a large area of study.
>

> The fitting source code for the web site is athttp://code.google.com/p/pyeq2/downloads/list

[zunzun.com]

Gompertz is not an algorithm.

To find some ground theory, find a book on curve fitting - there are several good ones.  From Amazon.com: http://www.amazon.com/s?ie=UTF8&keywords=curve%20fitting&rh=n%3A283155%2Ck%3Acurve%20fitting

I do not understand your Excel question.  I may not be able to help you, as I do not use Excel for curve fitting.

     James

[Dicky]

Whoa, reading a statistics book is kinda stretching as I am not an
expert on math. lol . My ability maybe just average. :)

Maybe I need to restate the question cause the last one is quite
confusing,
There is a just few thing i want to ask, I hope you could help me in
this.
1.
When I ask the previous question, I just hope to found some
"Sentences" that can become
a Ground Theory when I use some regression method from zunzun
especially for gompertz, exponential, power method.
--Because until today, I cannot found how to calculate variable a, b,
c from those method that Fit with zunzun result.--

2.
You once said " Uses a genetic algorithm, levenberg-marquardt,
downhill simplex",
Could you please explain when zunzun use these algorithm??
Are this sentence work all method on zunzun or only some certain
method??

I really hope that you could give me some explanation on those 2
question.
Though, I hope not to be too much bother though :p.
Thank you very much.

On Mar 14, 2:51 pm, "zunzun.com" <zunzun....@gmail.com> wrote:
> Gompertz is not an algorithm.
>
> To find some ground theory, find a book on curve fitting - there are

> several good ones.  From Amazon.com:http://www.amazon.com/s?ie=UTF8&keywords=curve%20fitting&rh=n%3A28315...

[zunzun.com]

1) For equations that are not linear in their coefficients, such as Gompertz, I use nonlinear fitting methods as I previously discussed.  That is how variables a, b and c are calculated.

 

2) These methods are used when fitting equations that are not linear in their coefficients.

 

This is a large and complicated area of study.  Please read a book on curve fitting for more detail.

 

     James