Re: NonlinearRegress fitfail error

• To: mathgroup at smc.vnet.net
• Subject: [mg89377] Re: NonlinearRegress fitfail error
• From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
• Date: Sat, 7 Jun 2008 03:00:59 -0400 (EDT)
• References: <g2b4pu\$nn4\$1@smc.vnet.net>

```Hi,

Needs["NonlinearRegression`"]

part1 = Table[{x,
With[{a2 = 2, b2 = -1, c2 = 1}, a2*(Exp[b2*x] - 1) + c2*x]}, {x,
0, 5, 0.05}];

startpoints = {a2, b2, c2};

msoln = BestFitParameters /.
NonlinearRegress[part1, a2*(Exp[b2*x] - 1) + c2*x, startpoints, x,
AccuracyGoal -> 5, PrecisionGoal -> 5, MaxIterations -> 5000,
Method -> "Gradient", RegressionReport -> BestFitParameters]

work fine.

Regards
Jens

Meaghan wrote:
> I'm updating an old program to Mathematica 6.  Here's the problem
> code:
>
> Needs["NonlinearRegression`"]
>
> msoln = BestFitParameters /.
>   NonlinearRegress[part1, a2*(Exp[b2*x] - 1) + c2*x, startpoints, x,
>    AccuracyGoal -> 5, PrecisionGoal -> 5, MaxIterations -> 500,
>    RegressionReport -> BestFitParameters]
> where "part1" is a long list of data points.
>
> I know this method of replacement was valid in 5.2, but here I get:
> FindFit::nrlnum: The function value {0.+(-1.+2.71828^(0. b2)) a2+0.
> c2,0.104632+(-1.+2.71828^(0.195816 b2)) a2+0.195816 c2,<<8>>,<<92>>}
> is not a list of real numbers with dimensions {102} at {a,b,c} =
> {0.0369002,0.32,0.158379}.
> NonlinearRegress::fitfail: The fitting algorithm failed.
> ReplaceAll::reps: "{msoln} is neither a list of replacement rules nor
> a valid dispatch table, and so cannot be used for replacing."
>
> Thank you for the help!
>

```

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