Re: Simultaneous Nonlinear Data Fits

*To*: mathgroup at smc.vnet.net*Subject*: [mg109275] Re: Simultaneous Nonlinear Data Fits*From*: TheBalrog <TheBalrogEE at gmail.com>*Date*: Tue, 20 Apr 2010 05:50:33 -0400 (EDT)

I am trying to do something similar but I'm afraid I don't understand all of the syntax or the expressions in either example. I'd like to post a notebook, but I'm not sure that it's possible on this forum. In Daniel's example, I cannot identify the expression, and thus cannot replace it with my own. It seems as though there are three expressions depending on the value of z (although I don't know what the zero means at the end of the If statement). Also in the FindFit[data,expr,pars,vars] command I do not know what x1,x2 and x3 refer to (are they related to x0?), nor do I understand how this expression relates to the previous one. In DanO's example I don't understand step 5. If the expression is myPeak, then why multiply it by KroneckerDelta[index-1]? Sorry for my ignorance but I'm not a mathematician. I enclose a function I am familiar with and two datasets I would like to fit; I have also written a Manipulate command so that anyone who would like to help can understand the expression. The independent variables are "S" and "Inh" and I would like to get a global solution for Vmax, Km and Ki. Naturally any help is greatly appreciated. data2D = {{0, 0}, {1, 2.5`}, {2, 3.5`}, {3, 3.8`}, {4, 4}, {0, 0}, {1, 1}, {2, 1.6`}, {3, 2.1`}, {4, 2.5`}}; data3D = {{0, 0, 0}, {0, 1, 2.5`}, {0, 2, 3.5`}, {0, 3, 3.8`}, {0, 4, 4}, {1, 0, 0}, {1, 1, 1.5`}, {1, 2, 2}, {1, 3, 2.3`}, {1, 4, 2.5`}}; expr = (Vmax (S))/((1 + Inh/Ki) Km + S); Manipulate[ Show[{Plot[(Vmax (S))/(Km (1 + (Inh/Ki)) + S), {S, 0, 4}, PlotRange -> {{0, 5}, {0, 5}}], ListPlot[data2D, PlotMarkers -> {\[FilledCircle], 10}]}], {Vmax, 0, 5}, {Km, 0, 5}, {Inh, 0, 1}, {Ki, 0.1, 1}]