Verify the File Path Check File Existence Verify File Permissions Check File Identifier Error Handling for File Openingwith thermo dta to matlab

clear all
close all
clc

% Define the file path
file_path = 'thermo.date';

% Attempt to open the file for reading
try
    f1 = fopen(file_path, 'r');   
    
    % Check if file opening was successful
    if f1 == -1
        error('Could not open the file.');
    end
    
    % Reading the comment lines
    for i = 1:5
        fgetl(f1);
    end

    % Extracting all species data

    for i = 1:53
        % Extracting name of gas species
        A = fgetl(f1);                  
        z = findstr(A, ' ');             
        species_name = A(1:z(1)-1);     

        % Extracting local temperatures of gas species
        t1 = str2double(A(z(1):z(2)));
        t2 = str2double(A(z(2):z(3)));
        t3 = str2double(A(z(3):end));

        % Extracting co-efficient of gas species
        B = fgetl(f1);                  
        a_values = sscanf(B, '%f');  
        a1 = a_values(1);
        a2 = a_values(2);
        a3 = a_values(3);
        a4 = a_values(4);
        a5 = a_values(5);

        C = fgetl(f1);
        a_values = sscanf(C, '%f');  
        a6 = a_values(1);
        a7 = a_values(2);
        a8 = a_values(3);
        a9 = a_values(4);
        a10 = a_values(5);

        D = fgetl(f1);
        a_values = sscanf(D, '%f');  
        a11 = a_values(1);
        a12 = a_values(2);
        a13 = a_values(3);
        a14 = a_values(4);

        % Creating the range of low and high values of local temperatures
        T = linspace(t1, t3, 1000);

        R = 8.314;  % Universal gas constant in J/mol.K

        % Calculation for Specific heat, Enthalpy and Entropy
        for j = 1:length(T)
            if T(j) > t2
                Cp(j) = (a1 + a2*T(j) + a3*T(j)^2 + a4*T(j)^3 + a5*T(j)^4)*R;
                H(j) = (a1 + (a2*T(j))/2 + (a3*T(j)^2)/3 + (a4*T(j)^3)/4 + (a5*T(j)^4)/5 + (a6/T(j)))*R*T(j); 
                S(j) = a1*log(T(j)) + a2*T(j) + (a3*T(j)^2)/2 + (a4*T(j)^3)/3 + (a5*T(j)^4)/4 + a7;
            else
                Cp(j) = (a8 + a9*T(j) + a10*T(j)^2 + a11*T(j)^3 + a12*T(j)^4)*R;
                H(j) = (a8 + (a9*T(j))/2 + (a10*T(j)^2)/3 + (a11*T(j)^3)/4 + (a12*T(j)^4)/5 + (a13/T(j)))*R*T(j); 
                S(j) = a8*log(T(j)) + a9*T(j) + (a10*T(j)^2)/2 + (a11*T(j)^3)/3 + (a12*T(j)^4)/4 + a14;
            end
        end

        % Molecular weight calculation
        elements = ['H', 'C', 'O', 'N', 'A', 'S'];                           
        atomic_weight = [1.0079 12.0107 15.999 14.0067 39.948 32.065];  
        mol_mass = 0;                                                   

        for l = 1:length(species_name)
            for m = 1:length(atomic_weight)
                if strcmp(species_name(l), elements(m))
                    mol_mass = mol_mass + atomic_weight(m);
                    position = m;
                end
            end
            n = str2double(species_name(l));
            if n > 1
                mol_mass = mol_mass + atomic_weight(position)*(n-1);
            end
        end

        % Printing the molecular weight of the gas species in the command window
        fprintf('Molecular Weight of %s is %f u\n', species_name, mol_mass);

        % Creating a folder to save the plots
        mkdir(species_name);         
        cd(species_name);   

        % Plotting specific heat vs temperature
        figure(1)
        plot(T, Cp, 'color', 'b', 'linewidth', 2)
        xlabel('Temperature (K)')
        ylabel('Specific Heat (J/K Kg)')
        title({'Specific Heat vs Temperature', ['Species name = ', species_name, ' & Molecular weight = ', num2str(mol_mass)]});
        saveas(gcf, 'Cp_vs_Temp.png')

        % Plotting enthalpy vs temperature
        figure(2)
        plot(T, H, 'color', 'r', 'linewidth', 2)
        xlabel('Temperature (K)')
        ylabel('Enthalpy (J/K)')
        title({'Enthalpy vs Temperature', ['Species name = ', species_name, ' & Molecular weight = ', num2str(mol_mass)]});
        saveas(gcf, 'Enthalpy_vs_Temp.png')

        % Plotting entropy vs temperature
        figure(3)
        plot(T, S, 'color', 'g', 'linewidth', 2)
        xlabel('Temperature (K)')
        ylabel('Entropy (J/K)')
        title({'Entropy vs Temperature', ['Species name = ', species_name, ' & Molecular weight = ', num2str(mol_mass)]});
        saveas(gcf, 'Entropy_vs_Temp.png')

        % To change the current directory to the main folder
        cd('..');

    end

    % Close the file
    fclose(f1);

catch ME
    % Error handling for various reasons file cannot be opened
    switch ME.identifier
        case 'MATLAB:fopen:FileNotFound'
            disp('File not found. Please check the file path.');
        case 'MATLAB:fopen:PermissionDenied'
            disp('Permission denied. MATLAB does not have the necessary permissions to read the file.');
        case 'MATLAB:fopen:InvalidPermission'
            disp('Invalid file permissions. Please check file permissions.');
        case 'MATLAB:fopen:InvalidFid'
            disp('Invalid file identifier. Use fopen to generate a valid file identifier.');
        otherwise
            disp('An unknown error occurred while opening the file.');
            disp(ME.message);
    end
end

An unknown error occurred while opening the file.

Could not open the file.

[Walter Roberson]

Your try/catch spans all of the code. In theory, you could be catching another error.

[Stephen23]

Avoid calling CD in code: to import any file data and to save those images use absolute/relative filenames.

It is possible that your CD has changed the directory, then the code errors, and then you run again from a current directory that is not the one you expect to be in. It is best to avoid CD in code.

Avoid TRY around the entirety of your code: judging by the displayed messages you are intending it to catch file errors, but that is not really a good reason to hide all errors in your code. Much better to use a few ASSERT statements to check that the filedata is as expected.

Note that

elements = ['H', 'C', 'O', 'N', 'A', 'S'];

is just a more complex way of writing

elements = 'HCONAS';

Answer 1

[Walter Roberson]

    [f1, msg] = fopen(file_path, 'r');   
    
    % Check if file opening was successful
    if f1 == -1
        error('Could not open the file because: %s', msg);
    end