MathGroup Archive 1996

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

Search the Archive

fitting a curve by adjusting exponents



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


  • Prev by Date: fitting a curve by adjusting exponents
  • Next by Date: Re: Subscripts in Text
  • Previous by thread: fitting a curve by adjusting exponents
  • Next by thread: Re: fitting a curve by adjusting exponents