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MathGroup Archive 1996

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Is there a bug in FIT?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg4379] Is there a bug in FIT?
  • From: welter at .ti.com (Jason Welter)
  • Date: Mon, 15 Jul 1996 08:01:24 -0400
  • Organization: Texas Instruments
  • Sender: owner-wri-mathgroup at wolfram.com

I am trying to fit some data and have discovered that the
FIT function does'nt work with the following data:

data1 = {{1.42 10^13, -1.26}, {1.5 10^13, -1.3}, {1.63 10^13, -1.37}};

When I do:

funcdata1 = Fit[data1,{1,x},x];

Show[{Plot[data1,{x,1.42 10^13,1.63 10^13}],ListPlot[data1]},
Prolog->AbsolutePointSize[16]]

I get terrible results, but when I take the exponents out:

data2 = {{1.42, -1.26}, {1.5, -1.3}, {1.63, -1.37}};

an I do:

funcdata2 = Fit[data2,{1,x},x];

Show[{Plot[data2,{x,1.42,1.63}],ListPlot[data2]},
Prolog->AbsolutePointSize[16]]

It fits it just fine.  What is wrong?


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