How to estimate a function that fit well with a curve

Click For Summary

Discussion Overview

The discussion revolves around methods for estimating a function that fits well with a given curve, focusing on curve fitting techniques and software options. Participants explore various mathematical approaches and tools for achieving better curve fitting, particularly in the context of data with significant variation.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant seeks advice on how to derive a function that fits a specific curve, sharing a link to the curve image.
  • Another participant suggests the LOESS method as a potential solution for curve fitting.
  • A participant mentions successfully using a fourth-degree polynomial in Excel for fitting but expresses concern about its effectiveness with more variable graphs, indicating a search for software that employs alternative methods like moving averages or exponential functions.
  • One participant critiques the use of polynomials for fitting, particularly in regions of steep slopes, and suggests that coordinate transformations or LOESS might yield better results.
  • A participant shares a link to an Excel add-in that claims to have LOESS capabilities and proposes considering parametric cubic polynomials, such as Bezier curves, for handling vertical slopes.
  • A later reply expresses gratitude for the shared information, noting that it provided a very good fitting solution.

Areas of Agreement / Disagreement

Participants express differing opinions on the effectiveness of polynomial functions for curve fitting, with some advocating for alternative methods like LOESS or parametric cubic polynomials. The discussion does not reach a consensus on the best approach.

Contextual Notes

Participants highlight limitations of polynomial fitting in certain regions of the curve and the potential need for coordinate transformations or alternative fitting methods, but do not resolve these issues.

gibnem
Messages
3
Reaction score
0
hello
somme one know how to get the function that fit well with a curve
following is my curve:
[PLAIN]http://img814.imageshack.us/img814/5885/tempdepth.png

thx..:smile:
 
Last edited by a moderator:
Mathematics news on Phys.org
http://en.wikipedia.org/wiki/LOESS" ?
 
Last edited by a moderator:
yeh it could be...

i could create a function that fit very well withe that graph just in excel with a fourth polynomiale and i get the numerical expresion
but withe some other graphe with more variation the polynomiale function don't fit very good so I'm looking if i can found a softwar thar use other methodes (moving average, exp, or a mix of this methodes) to get a better curve fitting)
 
A polynomial is not going to deal well with either the nearly vertical part at high depths, or the nearly horizontal part at low depths. You might be able to fix that with an appropriate coordinate transformation, but a generic method like LOESS will likely produce better results with less effort.
 
Here is a link to an Excel add-in that claims to have LOESS capability.

http://www.fileguru.com/Data-Curve-Fit-Creator-Add-in/download

If I were doing this I'd consider some form of parametric cubic polynomials (e.g. Bezier) because they can handle vertical slopes.
 
Last edited:
oooh thank you hotvette
that give a really a very very good fitting
 

Similar threads

  • · Replies 1 ·
Replies
1
Views
1K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 18 ·
Replies
18
Views
5K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 12 ·
Replies
12
Views
2K
  • · Replies 11 ·
Replies
11
Views
4K
  • · Replies 4 ·
Replies
4
Views
6K
Replies
7
Views
2K
  • · Replies 6 ·
Replies
6
Views
3K
  • · Replies 18 ·
Replies
18
Views
3K