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Re: Find a dood function for fitting data

  • To: mathgroup at smc.vnet.net
  • Subject: [mg42134] Re: [mg42096] Find a dood function for fitting data
  • From: "Mihajlo Vanevic" <mvane at eunet.yu>
  • Date: Fri, 20 Jun 2003 04:57:32 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Is this good enaugh??


In[]:=
<< Statistics`NonlinearFit`

In[]:=
data = {{0.5, 0.089}, {0.7, 0.12}, {1, 0.1652}, {2, 0.254}, {3, 0.3}, {4, 
        0.325}, {5, 0.34}, {7, 0.35}, {10, 0.35}, {15, 0.33}, {20, 0.32}};

In[]:=
f[x_] = NonlinearFit[data, 
    a1*(Exp[-b1*x] - Exp[-b2*x]), {x}, {{a1, 1.}, {b1, 2.}, {b2, 1.}}, 
    RegressionReport -> BestFitParameters]

In[]:=
Plot[f[x1], {x1, 0.5, 20}, 
  Epilog -> {Hue[0.], PointSize[0.02], Map[Point, data]}, PlotRange -> All]

In[]:=
data1 = {{0.5, 0.11}, {0.7, 0.15}, {1, 0.2112}, {2, 0.322}, {3, 0.37}, {4, 
        0.391}, {5, 0.399}, {7, 0.4}, {10, 0.38}, {15, 0.36}, {20, 0.33}};

In[]:=
f1[x_] = NonlinearFit[data1, 
    a1*(Exp[-b1*x] - Exp[-b2*x]), {x}, {{a1, 1.}, {b1, 2.}, {b2, 1.}}, 
    RegressionReport -> BestFitParameters]

In[]:=
Plot[f1[x1], {x1, 0.5, 20}, 
  Epilog -> {Hue[0.], PointSize[0.02], Map[Point, data1]}, PlotRange -> All]


Regards,				 
         Mihajlo Vanevic

**************************************************************
*    At 2003-06-19, 03:59:00 
*        guillerm, guillerm at usal.es  wrote:
**************************************************************
>(*Dear friend, I want fit these  data *)
>
>data = {{0.5, 0.089}, {0.7, 0.12}, {1, 0.1652}, {2, 0.254}, {3, 0.3}, {
>        4, 0.325}, {5, 0.34}, {7, 0.35}, {10, 0.35}, {15, 0.33}, {20, 0.32}};
>
>(*I have tested with a few function such as that the follow, but I 
>      have not found a good fit*)
>
>Needs["Statistics`NonlinearFit`"];
>
>fit[x1_] = NonlinearFit[data, a1 x1^b1 Exp[b2 x1], {x1}, {a1, b1, b2}]
>
>Plot[fit[x1], {x1, 0.5, 20}, Epilog -> Map[Point, data]]
>
>(*I have the same problem with this other data*)
>
>data1= {{0.5, 0.11}, {0.7, 0.15}, {1, 0.2112}, {2, 0.322}, {3, 0.37}, {4, 
>0.391}, {5, 0.399}, {7, 0.4}, {10, 0.38}, {15, 0.36}, {20, 0.33}};
>
>(*I will appreciate if you find a good fit, with no many parameters, for both 
>data. Thanks
>Guillermo
>Sanchez*)
>
>---------------------------------------------
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**************************************************************






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