Curve fitting algorithm

Hi

I have recently been impressed with the fitting of lines to many thousands
of data points in Excel when displaying this information on a chart, and am
wondering if anyone knows the algorithm that is used to make decisions about
the types of curves (e.g. simple polynomials, splines, Bezier...) used with a
particular data set?

Thanks

Ringo

I don't know that there's an "algorithm" for making that sort of judgement. A few things that probably should be considered:

1) Am I looking for an interpolating scheme (splines and Bezier curves) where each data point is considered to be exact and I'm using those algorithms to estimate values between the exact data points.
2) Am I curve fitting where each data point isn't necessarily exact but is considered to be representative of the process/phenomenon I am observing.
3) When selecting the form of equation to use in curve fitting, what do I know about the underlying process to which the data pertain? Should it be linear? Quadratic? Exponential growth/decay? Is there an asymptote?

A statistics text should discuss some of these issues as they relate to generic curve fitting. Any information you can gather relative to a specific problem can help answer specific questions. A numerical methods text should discuss the mechanics of curve fitting.

Take a look at Brian Murphy's work at
http://xlrotor.com/resources/files.shtml

Scroll down the page for the XL stuff.

--
Regards,

Tushar Mehta
www.tushar-mehta.com
Excel, PowerPoint, and VBA add-ins, tutorials
Custom MS Office productivity solutions

In article <10561B57-0D49-4BFA-B60A-165CC9892BFE@microsoft.com>,
ringo@discussions.microsoft.com says...
> Hi
>
> I have recently been impressed with the fitting of lines to many thousands
> of data points in Excel when displaying this information on a chart, and am
> wondering if anyone knows the algorithm that is used to make decisions about
> the types of curves (e.g. simple polynomials, splines, Bezier...) used with a
> particular data set?
>
> Thanks
>
> Ringo
>

Many thanks Tushar, that answers my question!

Ringo

"Tushar Mehta" wrote:

> Take a look at Brian Murphy's work at
> http://xlrotor.com/resources/files.shtml
>
> Scroll down the page for the XL stuff.
>
> --
> Regards,
>
> Tushar Mehta
> www.tushar-mehta.com
> Excel, PowerPoint, and VBA add-ins, tutorials
> Custom MS Office productivity solutions
>
> In article <10561B57-0D49-4BFA-B60A-165CC9892BFE@microsoft.com>,
> ringo@discussions.microsoft.com says...
> > Hi
> >
> > I have recently been impressed with the fitting of lines to many thousands
> > of data points in Excel when displaying this information on a chart, and am
> > wondering if anyone knows the algorithm that is used to make decisions about
> > the types of curves (e.g. simple polynomials, splines, Bezier...) used with a
> > particular data set?
> >
> > Thanks
> >
> > Ringo
> >
>

You are welcome. Glad to be of help.

--
Regards,

Tushar Mehta
www.tushar-mehta.com
Excel, PowerPoint, and VBA add-ins, tutorials
Custom MS Office productivity solutions

In article <71FB090B-0E98-4D07-B628-FDAF744EECB6@microsoft.com>,
ringo@discussions.microsoft.com says...
>
> Many thanks Tushar, that answers my question!
>
> Ringo
>
{snip}