Re: Curve-fitting/data analysis question...
- To: mathgroup at smc.vnet.net
- Subject: [mg73351] Re: Curve-fitting/data analysis question...
- From: "Robert Dodier" <robert.dodier at gmail.com>
- Date: Tue, 13 Feb 2007 07:01:23 -0500 (EST)
- References: <eqmcfh$bdv$1@smc.vnet.net>
On Feb 10, 11:18 pm, "sherifffruitfly" <sherifffruit... at gmail.com> wrote: > I've got some data that is approximately constant, c, over an > interval, and then drops off like -(a exp(b x)). > > How can I determine when the constant part ends, and the negative > exponential begins in Mathematica? I can eyeball it on a graph, but I'd much > prefer to have a principled Mathematica routine settle the question. Once > that's settled, it should be straightforward to determine the > exponential's parameters via some curve-fitting routine or other. See Seber & Wild, "Nonlinear Regression", Wiley, 1989 (iirc). They have a chapter on problems of this kind. I'm sure there are more recent refs, but I don't know any. I suspect that an automated procedure cannot do much better than you can do it by eye. If, however, you need to solve a collection of such problems and you need to automate the process, then an automated method can save you some time (without affecting the results much). FWIW Robert Dodier