Re: Nonlinear fit for a non-differentiable function
- To: mathgroup at smc.vnet.net
- Subject: [mg43149] Re: Nonlinear fit for a non-differentiable function
- From: "Bill Bertram" <wkb at aansto.gov.au>
- Date: Thu, 14 Aug 2003 05:08:07 -0400 (EDT)
- Organization: Australian Nuclear Science and Technology Organisation
- References: <bhd94f$rn9$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
"Ahmed Sayeed" <Ahmed.Sayeed at Tu-Ilmenau.De> wrote in message news:bhd94f$rn9$1 at smc.vnet.net... > Hello friends, > I have to carry out a nonlinear fit where the fit function is non-differentiable w.r.t. one or > more of the parameters, because I have to take the absolute value in the definition of the function. > For example, f[x_,a_,b_]:=a*Sin[Abs[b]*x], where a and b are fit parameters. NonlinearRegress > fails, giving the following message: Hello Ahmed, My solution to this kind of problem, which has worked for me, is to replace the variable by its square. Instead of f[x_,a_,b_]:=a*Sin[Abs[b]*x] you now fit the function f[x_,a_,c_]:=a*Sin[c^2 * x] . Cheers, Bill