Modeling concentration using ODE

Question

Stark Volt 2021-9-26

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1461089-modeling-concentration-using-ode

回答： Sulaymon Eshkabilov 2021-9-29

test_data.zip

I'm trying to model a dye concentration but I cannot make to run and I'm stuck. It gives an error but it will not tell what is wrong. Can any one help thanks?

clear all; 
data = load('test_data.dat');
Error using load
Unable to find file or directory 'test_data.dat'.
time  = size(data,1);
u = data(:,2);
tspan = [1:1:time];
y0  = data(1,3);
f  = -0.25; 
g  = 0.25; 
T = 10.0; 
[t,y]=ode45(@model,tspan,y0,f,g,T,U);
plot(t, y(:,end), '*-b', 'LineWidth', 1);
function dydt = model(t,y,f,g,T,u)
if t-1 <= T
    u = 0;
else
    t_back = t-T;
    n = floor(t_back); u =(n);
end
dydt = f*y + g*u;
return;
end

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Image Analyst 2021-9-26

在 MATLAB Online 中打开

What is option? It says it's not defined. If I use options instead of option, I just get more errors.

clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
imtool close all;  % Close all imtool figures if you have the Image Processing Toolbox.
clear;  % Erase all existing variables. Or clearvars if you want.
workspace;  % Make sure the workspace panel is showing.
format short g;
format compact;
fontSize = 20;
%(the .mlx file)
%Dye concentration
clear all; 
data = load('test_data.dat');
time  = size(data,1);	% simulation time
input = data(:,2);		% measured top concentration
rslt  = data(:,3);      % measured bottom concentration
tspan = [1:1:time]; % time variable
inc  = data(1,3);  % initial bottom concentration
%model parameters
fparameter  = -0.25; 
gparameter  = 0.25; 
delay = 10.0; 
options = odeset('RelTol', 1e-3);
[t,y]=ode45(@model,tspan,inc,option);
plot(tspan, obsv, '-b', 'LineWidth', 0.5); hold on; 
plot(tspan, input, '-g', 'LineWidth', 0.5);
plot(t, y(:,end), '-.m', 'LineWidth', 1);
legend('rslt', 'input');
xlabel('time(second)'); ylabel('Concentration');
grid;
%Predefined function (the .m file)
function dydt = model(t,y,parameter,input)
% MODEL ordinary differential equation (ODE) model:
%          dy/dt = f*y(t) + g*u(t-T)
dxdt = 0;%return variables
if t-1 <= parameter(3) %delay the initial concentration
    u_input = 0;
else
    t_back = t-parameter(3);
    n = floor(t_back); u_input = input(n);
end
dydt = f*y(t) + g*u(t-T)
return;
end

Stark Volt 2021-9-28

hello @ Star rider, after I did go through the link you provided which made me read other mathlab knowlegde and documentation so I revise the code that I posted but it I still can't figure out what is wrong. Here are the error poping up thanks.

Not enough input arguments.

Error in cstr_model (line 19)

n = floor(t_back); u= u(n);

Error in odefcncleanup>@(t,y)oldFcn(t,y,inputArgs{:}) (line 11)

newFcn = @(t,y) oldFcn(t,y,inputArgs{:});

Error in ode45 (line 299)

f2 = odeFcn_main(t2, y2);

Error in hw3 (line 33)

[t, x] = ode45(@cstr_model,tspan, y0,f,g,T,u);

**so in the this error newFcn = @(t,y) oldFcn(t,y,inputArgs{:}); what does this mean inputArgs{:}? thank you.

Star Strider 2021-9-29

Please provide a symbolic (preferably LaTeX) version of the differential equation system you’re working with, and the parameters you want to estimate. If you have a PDF of a paper describing what you want to do, that would be even better. (Attach / upload the PDF, not a link to it, because thery’re usually behind a paywall, preventing me from accessing them if I don’t subscribe to the journal.)

Also, putting if blocks in the differential equation function is going to cause problems. Numerical differential equation integration functions don’t do well when integrating across the discontinuities that the if blocks cause.

I don’t understand the reason ‘parameter’ is nowhere represented in the differential equation.

I’ll do my best to see if I can get the differential equation (or system of them) to work with my code and your data.

.

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Answer 1

Sulaymon Eshkabilov 2021-9-29

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1461089-modeling-concentration-using-ode#answer_797379

在 MATLAB Online 中打开

You had better use this data importing fcn:

data = readmatrix('test_data.dat');

Make sure that the data file (test_data.dat) is present in your current directory or change to the directory where the data file (test_data.dat) is residing.

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Modeling concentration using ODE

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