iteration of parameter of a system of ode's using lsqnonlin, version2

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helen flountzi 2017-1-17

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/320800-iteration-of-parameter-of-a-system-of-ode-s-using-lsqnonlin-version2

回答： Matt J 2017-1-17

I want to iterate a parameter estimation -for example 20 times, using different data points-which comes from lsqnonlin command.The parameter is used in a couple of ODEs.The first code is:

%%Main code
% Guess what beta might be. Note: lb = lower bound, ub = upper bound
  beta0 = 0.001;
  beta_lb = 0;
  beta_ub = 0.01;
% This means that nothing is output to the display after the fit. Can be
% changed if necessary.
  opts = optimset('display','off');
% Fit the parameter to the system of equations with this initial guess
  fitted_parameter_beta = lsqnonlin(@(p) model_fit_r(p), beta0, beta_lb, beta_ub, opts);
% Display the fitted parameter, here, beta
  disp('Fitted parameter beta')
  disp(fitted_parameter_beta)

and the second file with the function is:

%%This file calculates the difference between the model and the data
function fitting_function = model_fit(p)
% Set the parameter to be fit (note that p can be a vector)
beta_fit = p;
% Data point - This is the data that the beta_fit parameter will try
% to fit to and it can be changed 
  _data = 0.11;  %For example, 11%  at end timepoint
  tspan = 0:0.5:100;
y0 = [98, 2];
  [~,y] = ode45(@(t,y) model_fitting_equations(t,y,beta_fit),tspan,y0);
calculation_model = y(end,2)/(y(end,1)+y(end,2)); 
% Find the difference between the model and the data - 
  fitting_function = calculated_by_model - _data;
end

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Stephen23 2017-1-17

编辑：Stephen23 2017-1-17

@helen flountzi: do not keep adding new questions to this forum with exactly the same question but more details. You can simply edit your question or add comments.

I deleted your other question which you edited away. Please do not edit away text of your question: this makes it hard for us to help you.

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Star Strider 2017-1-17

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/320800-iteration-of-parameter-of-a-system-of-ode-s-using-lsqnonlin-version2#answer_250931

Your code is difficult for me to follow, and you haven’t described what the problem is, only that you want to fit the points.

In ‘model_fit’, is ‘calculation_model’ the same as ‘calculated_by_model’ or something different? That could be the problem if they are supposed to be the same variable.

See if the approaches in:

Monod kinetics and curve fitting

or:

Parameter Estimation for a System of Differential Equations

would help you do what you want.

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helen flountzi 2017-1-17

yes it is the same, sorry for that and it is not the problem, I reasure you!The problem is that I want to repeat this estimation procedure many times and get many estimation, and I always get error messages