FindFit issue
- To: mathgroup at smc.vnet.net
- Subject: [mg86395] FindFit issue
- From: t.dubaj at gmail.com
- Date: Mon, 10 Mar 2008 02:04:34 -0500 (EST)
Hi,
I am trying to fit experimental data
d = {{1000, 44.576*10^(-3)},
{600, 49.546*10^(-3)},
{800, 46.757*10^(-3)},
{400, 55.023*10^(-3)},
{200, 61.209*10^(-3)},
{10, 71.584*10^(-3)},
{100, 65.367*10^(-3)}}
and model is:
y = 0.072214 - a*Log[10, 1+b*x]
but Mathematica after typing
FindFit[d, 0.072214 - a*Log[10, 1 + b*x], {a, b}, x]
return
FindFit::nrlnum: The function value {-0.0226973-0.0208168 \
\[ImaginaryI],<<5>>,-0.0282009-<<21>> \[ImaginaryI]} is not a list of
\
real numbers with dimensions {7} at {a,b} = {0.0152574,-1.99204}.
{a -> 0.0152574, b -> -1.99204}
(especialy value of "b" is really awful - negative number in Log)
But I know, there is Fit (calculated in Scientist) with coefficients
a = 0.033706
b = 0.0057934
Can someone explain what I'm doing wrong?
Best regards,
T.D.
- Follow-Ups:
- Re: FindFit issue
- From: Darren Glosemeyer <darreng@wolfram.com>
- Re: FindFit issue