Hi Abrar,
From my understanding you want to convert the given .txt file into a MATLAB function that defines the system of ODEs.
To achieve this, you need to parse the equations to extract the parameters and terms, then compose and write this processed information into a new MATLAB function file.
Below is the code for it:
% Define the filename of the text file containing the equations
filename = 'file_name.txt';
% Open the file and read the contents
fileID = fopen(filename, 'r');
if fileID == -1
error('File not found or permission denied');
end
fileContents = fscanf(fileID, '%c');
fclose(fileID);
% Split the contents by lines (assuming each equation is on a new line)
equations = strsplit(fileContents, '\n');
% Initialize an empty cell array for the ODE system
odeSystem = {};
% Loop through each equation and parse it
for i = 1:length(equations)
eq = strtrim(equations{i}); % Remove leading/trailing whitespace
if isempty(eq)
continue; % Skip empty lines
end
% Replace 'P' with 'N(1)' and 'H' with 'N(2)'
eq = strrep(eq, 'P', 'N(1)');
eq = strrep(eq, 'H', 'N(2)');
% Remove 'dP/dt=' and 'dH/dt='
eq = regexprep(eq, 'd[PN]\(?\d?\)?\/dt=', '');
% Ensure multiplication is explicit
eq = regexprep(eq, '(N\(\d\))([a-zA-Z])', '$1*$2');
eq = regexprep(eq, '([a-zA-Z])(N\(\d\))', '$1*$2');
% Add the parsed equation to the ODE system
odeSystem{end+1} = eq;
end
% Construct the function definition
functionDef = 'function dNdt = PredPrayDynamics_ODE(t, N)';
% Join the equations with a semicolon and a newline character
functionBody = strjoin(odeSystem, ';...\n ');
% Construct the body with the joined equations
functionBody = sprintf('dNdt = [%s];', functionBody);
functionEnd = 'end';
% Combine the function definition, body, and end to form the complete function
completeFunction = sprintf('%s\n%s\n%s', functionDef, functionBody, functionEnd);
% Display the function
disp(completeFunction);
% Write the function to a .m file
funcFilename = 'PredPrayDynamics_ODE.m';
funcFileID = fopen(funcFilename, 'w');
if funcFileID == -1
error('Could not create output function file');
end
fprintf(funcFileID, '%s', completeFunction);
fclose(funcFileID);
Please refer to the links below to learn more about parsing equations, regular expressions and string operations that were used in the above code.
I hope this helps!
Sameer
