Re: [Q] How to use NonlinearFit[...]
- To: mathgroup at christensen.cybernetics.net
- Subject: [mg902] Re: [Q] How to use NonlinearFit[...]
- From: rubin at msu.edu (Paul A. Rubin)
- Date: Sun, 30 Apr 1995 03:36:31 -0400
- Organization: Michigan State University
In article <3n9shi$poj at news0.cybernetics.net>,
dave at freebucks.feinberg.nwu.edu (David Johnson) wrote:
->
->I have a set of data that I would like to fit to an equation
->using the following initial equation: x[[n+1] = A x[[n]] ( 1 - B X[[n]])
->This is a typical nonlinear, dynamical equation used in many texts
->as a function that may interate equations to chaotic states.
->
->Several people have suggested I use NonlinearFit in the Nonlinear
package.
->I haven't any clue how to set up this for NonlinearFit.
->I know I must be missing something simple but how can I use NonlinearFit
to
->finds the best fit for an equation who's next data point is the result of
->its current fit? Please excuse my lack of good english communication to
->communicate what I want, I just hope it's understandable.
->
->Has anyone a suggestion or a Mathematica text reference.
->
Lets say x is a vector of length n containing your data, with the oldest
observation in x[[1]]. Try something like this (after loading
NonlinearFit):
NonlinearFit[
Transpose[ {Drop[ x, -1 ], Drop[ x, 1 ]} ],
a z (1 - b z), z, {a, b}
]
Your independent and dependent variables are x with the newest respectively
oldest observations removed.
Paul
**************************************************************************
* Paul A. Rubin Phone: (517) 432-3509 *
* Department of Management Fax: (517) 432-1111 *
* Eli Broad Graduate School of Management Net: RUBIN at MSU.EDU *
* Michigan State University *
* East Lansing, MI 48824-1122 (USA) *
**************************************************************************
Mathematicians are like Frenchmen: whenever you say something to them,
they translate it into their own language, and at once it is something
entirely different. J. W. v. GOETHE