Re: Help with an error with NonlinearModelFit, Mathematica 7.0

*To*: mathgroup at smc.vnet.net*Subject*: [mg99579] Re: Help with an error with NonlinearModelFit, Mathematica 7.0*From*: Peter Pein <petsie at dordos.net>*Date*: Fri, 8 May 2009 00:17:26 -0400 (EDT)*References*: <gtudh6$it8$1@smc.vnet.net>

Anonymous schrieb: > I'm trying to find a fit to a large set of data. > > Here are In[1], In[2]. > > In[1] := {{421.1, 6591.10}, ...}; > > (there are way more points, in fact there are 35 in total, but I don't > want to list them. All are real numbers.) > > In[2] := nlm = NonlinearModelFit[data, Log[ak^2 + bk + c], {a,b,c}, k] > > Then mathematica gives an error that basically says that the function > "is not a list of real numbers" > > Of course it is, so how do I fix this? > Hi, I can't reproduce this message using Mathematica 6: In[1]:= data = Transpose[{#,Log[#^2-#+2]+Random[]/10}&[RandomReal[{0,500},{35}]]]; In[2]:= nlm=FindFit[data,Log[a k^2+b k+c],{a,b,c},k] Out[2]= {a->1.04002,b->-1.04002,c->2.08004} => either it is a bug in version 7 or your data leads to some Logs of negative numbers. Please submit the list. Peter