Re: Exponetial Fit
- To: mathgroup at christensen.cybernetics.net
- Subject: [mg1823] Re: Exponetial Fit
- From: hsh104 at psu.edu (Hein Hundal)
- Date: Thu, 3 Aug 1995 23:52:06 -0400
- Organization: CAC
In article <3ui5dj$231 at news0.cybernetics.net> crunch at s-cwis.unomaha.edu (John L. White) writes:
> I have tried to do a exponetial fit to a list of data from a physics
>experiment, but Mathematica does a terrible job when I do the following
>command:
>Exp[Fit[Log(data),{1,t},t]]
Depending on what you mean by an exponential fit, there are some better
ways.
If you want to find the best fit of the form y = A Exp[B x], try
logy[{x_,y_}] := {x, Log[y]}
logpoints = Map[logy, points] //N
Exp[Fit[logpoints, {1,x}, x]]
This gives the correct answer for
points = {{1, 3 Exp[2]}, {2, 3 Exp[4]}, {3, 3 Exp[6]}}
(* f[x] = 3 Exp[2 x] *)
If you want to find the best fit of the form y = A x^B, try
logpoints = Map[logy, points] //N
Exp[Fit[logpoints, {1, Log[x]}, x]]
This gives the correct answer for
points = {{1, 3}, {2, 12}, {3, 27}, {4, 48}}
(* f[x] = 3 x^2 *)
I hope that helps. - Hein Hundal