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Topic: Help: Problems with fitting a list of data with an equation with two parameters
Replies: 3   Last Post: Feb 12, 2013 3:23 AM

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 dinodeblasio@gmail.com Posts: 23 Registered: 10/14/07
Help: Problems with fitting a list of data with an equation with two parameters
Posted: Feb 6, 2013 1:50 AM
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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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