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! >