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

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

[Stephen23]

@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.

Answer 1

[Star Strider]

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.

[helen flountzi]

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

[Star Strider]

If you would be so kind as to share the error messages, it would be easier to help you.

Copy and paste all the red text of the error messages from the Command Window to a Comment here, and format them as [{}Code].

Answer 2

[Matt J]

One reason that you might be getting errors is because of lines like this

_data = 0.11;

Variable names in MATLAB are not allowed to begin with underscores.