Re: optimizing

*To*: mathgroup at smc.vnet.net*Subject*: [mg74902] Re: optimizing*From*: dh <dh at metrohm.ch>*Date*: Tue, 10 Apr 2007 06:02:01 -0400 (EDT)*References*: <evabpk$df6$1@smc.vnet.net>

Hi, your model function has the form: Exp[-k t], no need to solve an DE. Now you have the model function and your data and you can e.g. use "FindFit" to get the obtimal k. Daniel kaiwan wrote: > Hi! I have to find the best parameter "k" with witch function sd[k]->minimum. I do that with FindMinimum. "sd" if a function that calculates the standard deviation from my experimental and model data. The model data is obtained from the mathematical model, first order differential equation...which I solve using NDsolve. The problem is that I cant make NDSolve work under FindMinimum. > > Something like this: > First, I define function that hace to solve the equation c'[t] == -k c[t], where "k" is a variable. This gives me model data later on. I define it as a function cause I dont know the value of "k" yet. > > Then I define another function which calculates the standard deviation: > sd[k_]:= function(model data, experimental data) > > Still I have no concrete results. > > Then I use FindMiniumm for finding the "k" that gives the smallest Standard Deviation > FindMinimum[sd[k], {k, 0.04}] > > And her is the problem, I cant make this combination to work .... help please? Many thanks! >