Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
1996
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*November
*December
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 1996

[Date Index] [Thread Index] [Author Index]

Search the Archive

fitting a curve by adjusting exponents

  • To: mathgroup at smc.vnet.net
  • Subject: [mg3254] fitting a curve by adjusting exponents
  • From: wself at viking.emcmt.edu (Will Self)
  • Date: Wed, 21 Feb 1996 02:14:58 -0500
  • Sender: owner-wri-mathgroup at wolfram.com

I'm sorry, I lost the original post.  Someone wanted to fit a function
of the form func[x,y,z,w] = a x^b + c y^d + e z^f + g w^h to some data
points.

Here's what I would suggest.  Write the usual expression ERR for the
sum of the squares of the errors.  Calculate the gradient of ERR
with respect to the 8 variables a through h.  Starting with your best
guess (from your physics) as to the actual values of the variables, 
do a gradient search to minimize the total error.  In doing the
gradient search, you might as well go ahead at each step and minimize
ERR + t*grad[ERR] as a function of t.

Will Self

==== [MESSAGE SEPARATOR] ====


  • Prev by Date: Re: Graphing recurrences
  • Next by Date: fitting a curve by adjusting exponents
  • Previous by thread: Re: SetOptions & Show
  • Next by thread: fitting a curve by adjusting exponents