Re: [Dev-C++] Curve fitting C++

[Thymian <Th...@gm...>]

Peter Hewitt schrieb:

> I have a few points on a graph, and would like a C++ function that 
> calculates a best fit equation such as a n degree polynomial.
>
> Are there functions already available to do this, or any ideas how I would 
> write one.
> I've checked on the web but can't seem to find anything useful.
>
> Thanks,
> Pete
>
>   


I recommend you to use a special form of polynomial interpolation, the 
"spline interpolation".
After understanding the mathematical background, it is relatively easy 
to implement a spline function into a given computer language like C or 
C++. Years ago I implemented it even in assembler for an embedded 
real-time system with very restricted hardware ressources, later in C, 
when RAM and EEPROM together with the 8/16-bit microcontroller become 
cheaper.


http://de.wikipedia.org/wiki/Spline

http://de.wikipedia.org/wiki/Spline-Interpolation


http://en.wikipedia.org/wiki/Spline_%28mathematics%29

http://en.wikipedia.org/wiki/Spline_interpolation




If you are too lazy to implement it by your own, you could try to use 
the GSL (GNU Scientific Library).

The GNU Scientific Library (GSL) is a numerical library for C and C++ 
programmers.
It is free software under the GNU General Public License.
The library provides a wide range of mathematical routines such as 
interpolation, polynomials, random number generators, special functions 
and least-squares fitting. There are over 1000 functions in total with 
an extensive test suite.

http://www.gnu.org/software/gsl/

http://www.gnu.org/software/gsl/manual/html_node/

http://www.gnu.org/software/gsl/manual/html_node/Interpolation.html




Another possibility for your purpose could be Scilab / Scicos, an "open 
source" scientific math package, IMHO written in C / C++ and its source 
code free available. You could try to extract pieces of the source code 
that you need.

http://en.wikipedia.org/wiki/Scilab




To try an example with your values (points in your graph) there is a 
spline calculator, written in Java, that you could take a look at:

http://www.arndt-bruenner.de/mathe/scripts/kubspline.htm#rechner




I hope your German is better then my English   ;-)

Gruß,
Werner Kitzmann



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