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Re: Help: Problems with fitting a list of data with an equation with

  • To: mathgroup at smc.vnet.net
  • Subject: [mg129715] Re: Help: Problems with fitting a list of data with an equation with
  • From: roby <roby.nowak at gmail.com>
  • Date: Wed, 6 Feb 2013 21:27:44 -0500 (EST)
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  • References: <kesug3$jun$1@smc.vnet.net>

Hi Dino,

As a first hint:

model = Solve[-A/(2 Sqrt[
           B^2 + 4 A B]) (Log[(2 A y^2 + b - 
            Sqrt[B^2 + 4 A B])/(2 A y^2 + b + Sqrt[B^2 + 4 A B])]) - 
      A/(2 Sqrt[
           B^2 + 4 A B]) (Log[(b - Sqrt[B^2 + 4 A B])/(b + 
            Sqrt[B^2 + 4 A B])]) == t, y][[1]] // FullSimplify



you can't youse {} as instead of () for groupung of expressions.

{} in Mathematica is used for arrays.


Further you must ensure that you choose a realvalued modell (not complex) before trying to fit.

Regards Robert


Am Mittwoch, 6. Februar 2013 07:50:43 UTC+1 schrieb dinode... at gmail.com:
> Hello everyone:
> 
> I'd like to fit a list like:
> 
> data2211={{0., 0.}, {1., 0.0000202672}, {2., 0.0000606506}, {3., 
> 
>   0.0000902571}, {4., 0.00011201}, {5., 0.000122325}, {6., 
> 
>   0.000129026}, {7., 0.000136861}, {8., 0.000138904}, {9., 
> 
>   0.000142179}, {10., 0.000145617}, {11., 0.000150792}, {12., 
> 
>   0.000153723}, {13., 0.000158662}, {14., 0.000163744}, {15., 
> 
>   0.000170338}, {16., 0.000176373}, {17., 0.000184436}, {18., 
> 
>   0.000191055}, {19., 0.000197175}, {20., 0.000205177}, {21., 
> 
>   0.000212824}, {22., 0.000221142}, {23., 0.000228844}, {24., 
> 
>   0.000236553}, {25., 0.000243398}, {26., 0.000251118}, {27., 
> 
>   0.000258642}, {28., 0.00026638}, {29., 0.000275992}, {30., 
> 
>   0.000284433}, {31., 0.000291682}, {32., 0.000300548}, {33., 
> 
>   0.000308275}, {34., 0.000316503}, {35., 0.000322813}, {36., 
> 
>   0.000332034}, {37., 0.000340994}, {38., 0.000349994}, {39., 
> 
>   0.00035922}, {40., 0.000366491}, {41., 0.00037264}, {42., 
> 
>   0.000379767}, {43., 0.000388169}, {44., 0.000395309}, {45., 
> 
>   0.000403434}, {46., 0.000411034}, {47., 0.00041769}, {48., 
> 
>   0.000424886}, {49., 0.000431168}, {50., 0.000437785}, {51., 
> 
>   0.000446171}, {52., 0.000453136}, {53., 0.000460042}, {54., 
> 
>   0.000467164}, {55., 0.000473857}, {56., 0.00047967}, {57., 
> 
>   0.00048695}, {58., 0.000492749}, {59., 0.000499251}, {60., 
> 
>   0.000506003}, {61., 0.000512512}, {62., 0.000516679}, {63., 
> 
>   0.000522183}};
> 
> 
> 
> with something like:
> 
> Clear[y];
> 
> Column[{model = 
> 
>     Solve[-A/(
> 
>          2 Sqrt[B^2 + 4 A B]) {Log[(2 A y^2 + b - Sqrt[B^2 + 4 A B])/(
> 
>            2 A y^2 + b + Sqrt[B^2 + 4 A B])]} - -A/(
> 
>          2 Sqrt[B^2 + 4 A B]) {Log[(b - Sqrt[B^2 + 4 A B])/(
> 
>            b + Sqrt[B^2 + 4 A B])]} == t, y[t], t][[1]], 
> 
>    param = FindFit[data1211, y[t] /. model, {A, B}, t], 
> 
>    Plot[y[t] /. model /. param, {t, 0, Max[data1211[[All, 1]]]}, 
> 
>     PlotRange -> All}]}] // Quiet
> 
> 
> 
> however there is some errors which I can't figure it out.
> 
> Any help is appreciated.
> 
> 
> 
> Thanks,
> 
> Dino




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