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MathGroup Archive 2004

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NonlinearFit problem

  • To: mathgroup at smc.vnet.net
  • Subject: [mg52033] NonlinearFit problem
  • From: Feng-Yin Chang <fychang at slac.stanford.edu>
  • Date: Mon, 8 Nov 2004 03:13:12 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

Hi All,
   Could anyone give me any suggestion for the specified  fitting function
   f= r^a Exp[-b r]?
   My data point was given below,
   data={{0, 1.00002}, {2.31507, 26.4522}, {4.32033, 56.8265}, {6.63539,
    59.6674}, {8.64066, 39.5536}, {10.9557, 21.6862}, {12.961,
    10.1456}, {15.276, 4.39652}}

  The following way,
   NonlinearFit[data,f,r,{a,b}], gives the error message,
   FindFit::njnum:
   The Jacobian is not a matrix of numbers at (a,b)={1.,1.}.

  How should I do this fitting without the problem?


Feng-Yin Chang,
Institute of Physics,NCTU,Taiwan


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