curvefit.txt

curve_fit为曲线拟合DELPHI源代码。此版本为delphi4或者delphi5源代码

This zip file contains a Delphi 4 (and 5) version of Allen Miller's Curve 
Fitting routine (from: the book "Pascal Programs For Scientists And 
Engineers", typed and submitted to MTPUG in Oct. 1982 by Juergen Loewner,
and corrected and adaptated for Turbo Pascal by Jeff Weiss.

I have updated these routines to work with  Delphi 4's open array 
parameters. which allows the routine to be generalised so that it is 
no longer hard-coded to make a specific order of best fit or work with 
a specific number of points.

The routine also works with Delphi 5 (and probably 6 and 7), and the 
testbed program runs under Delphi 5.  Ensure that the unit CurveFit.pas
is somewhere on the testbed's library path.

Richard Kavanagh ([e-mail]) kindly supplied a C++ version
which is included as the archive PolyFitC++.zip

RELEASE HISTORY

2003 Mar 05  Kelvin Lee spotted an error when all Y values were the same, 
             causing a divide by zero when calculating the correlation 
             coefficient.  Now fixed.
2003 Jun 12  Added missing PreCH.h include definitions to PolyFitC++.zip


HINTS

Warren Postma noted: 

  Can anyone suggest to me the proper way to calculate the solution for 
  fitting a set of (X,Y) pairs that is like the 1st order (linear) 
  equation y = mx + b, but forced through a certain value of b?

  Okay, it turns out that the Polyfit equation can be used for this, by 
  putting the data in twice (doubled), the first set of data is normal,
  the second set, all the X and Y values are multiplied by -1. This
  creates a "mirror image" of the data, and the curve that is fitted
  always goes through (0, 0).

Nice one, Warren!


David J Taylor, Edinburgh
2005 Feb 04
Web site: www.satsignal.net
E-mail: [e-mail]