Curve fitting algorithm

[Guest]

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

 

[MrShorty]

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.

 

[Tushar Mehta]

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

 

[Guest]

Many thanks Tushar, that answers my question!

Ringo

 

[Tushar Mehta]

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

Many thanks Tushar, that answers my question!

Ringo

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