Let's consider the following data:
data = Table[{q, 2*q^2}, {q, 0, 2}];
and then, do a very simple fitting to this data:
FindFit[data, a*q^b, {a, b}, q]
I get the answer:
Infinity::indet: Indeterminate expression 0. (-\[Infinity]) encountered. >>
FindFit::nrjnum: The Jacobian is not a matrix of real numbers at {a,b} = {1.,1.}. >>
Out[68]= {a -> 1., b -> 1.}
if we remove the {0,0}
point:
FindFit[Rest@data, a*q^b, {a, b}, q]
we correctly get:
{a -> 2., b -> 2.}
I've read this, which is very similar, but even if I hint it to start with the correct values, I get the same error message:
FindFit[data, a*q^b, {{a, 2}, {b, 2}}, q]
This would seem a too basic limitation of Mathematica 8 fitting algorithms, and so, before accusing it, what am I doing wrong?