Re: Exponential fit question.
- To: mathgroup at smc.vnet.net
- Subject: [mg27992] Re: Exponential fit question.
- From: "Paul Lutus" <nospam at nosite.com>
- Date: Wed, 28 Mar 2001 02:40:21 -0500 (EST)
- References: <99pdg6$lft@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
"joe" <joe at wam.umd.edu> wrote in message news:99pdg6$lft at smc.vnet.net... > hello. > > I was wondering if someone could help me with the following problem. > > I am trying to perform an exponential fit to the following data > {{x,y}} > > data > ={{50,22},{64,62},{78,122},{93,269},{107,414},{122,507},{136,597}} > > Fit[data,Exp[x],x] > > what I get is > > 1.94272422061017735^-63 *E^x Which is not correct. > > With Excel I get 7.5*E^0.0034x which is correct. > > How can I do this with Mathematica ? Excel's exponential regression method is not particularly useful, because it relies on a fractional power. This creates all kinds of problems in mathematical manipulations. Also, the result you posted doesn't fit the data very well at all -- have you tried to graph it in Excel to see how poorly it fits the data? If you do this, you will notice even a linear regression (y = m x + b) does a better job of fitting the data. Why not perform another kind of fit? Virtually any other fit is better suited to the data. -- Paul Lutus www.arachnoid.com