From: Osman.Buyukisik@ae.ge.COM (U-E59264-Osman Buyukisik)
Newsgroups: sci.math.symbolic
Subject: Re: non-linear curve fitting.
Date: 3 Jul 96 04:01:33 GMT

>>>>> "skypak" == skypak  <news.ysu.edu!news.cps.udayton.edu!news.engr.udayton.edu!blackbird.afit.af.mil!zombie.ncsc.mil!news.mathworks.com!newsfeed.internetmci.com!in2.uu.net!sangam!iitb!powai!skypak.@neoucom.edu> writes:

    skypak> Subject: non-linear curve fitting.

    skypak>  I NEED HELP IN DETERMINING THE CONSTANTS C1 THROUGH C4
    skypak> FOR THE FOLLOWING EQUATION FOR A SET OF X AND Y
    skypak> VALUES. THE EQUATION IS
 
    skypak> AS FOLLOWS
   
    skypak>      log y = C1 SINH [C2(LOG X + C3)] + C4
   
    skypak> THE TYPICAL VALUES OF X AND Y ARE

    skypak>            Y X (10E-6)

     
First : Don't use all caps!
Second : Get gnuplot 3.6 beta (check comp.graphics.apps.gnuplot). It has a "fit" function.
It is available for almost any platform. Here is what you may have to type:

f(x)=exp(c1*sinh(c2*log(x)+c3)+c4)
c1=1
c2=1
c3=1
c4=1
fit f(x) 'foo' via c1,c2,c3,c4
plot 'goo' title "data", f(x) title "fitted func"

And put your x,y data into the file 'foo', you'll get your answers.
You may have to give reasonable starting values intead of 1's.


Osman