'Power Law with singularity' regression - error

*To*: mathgroup at smc.vnet.net*Subject*: [mg130003] 'Power Law with singularity' regression - error*From*: dpi <deepankur.thureja at hotmail.com>*Date*: Sun, 3 Mar 2013 22:59:16 -0500 (EST)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*Delivered-to*: l-mathgroup@wolfram.com*Delivered-to*: mathgroup-newout@smc.vnet.net*Delivered-to*: mathgroup-newsend@smc.vnet.net

Hi, I am testing the "Power Law with finite-time singularity" hypothesis for the World population growth for a project. For that I was trying the following model: model = A + B*(c - x)^z; And then the following curve fit method: FindFit[data, {model}, {A, B, c, z}, x] But I always get the result: Power::indet: "Indeterminate expression 0.^0. encountered." FindFit::nrjnum: "The Jacobian is not a matrix of real numbers at {A,B,c,z} = {1.,1.,1.,1.}. " {A -> 1., B -> 1., c -> 1., z -> 1.} If I do a normal Power law regression, FindFit works perfectly, but the title of the project being "Power Law with finite-time singularity" I need to have a singularity in the model and the main aim is to find when this singularity occurs. Is there a way to use 'FindFit[]' to get the correct answer? Or Should I be using some other function? I have seen other articles on this site concerning issues with FindFit, but none of them has helped me resolve this problem. Thanks for the help!