opts = detectImportOptions Pass method when there is no variable Naming when reading more than 100 files

Background: Using opts = detectImportOptions, some file data are missing out of more than 100 files

Purpose: How to write after skipping the 25th file VariableName2 and skipping

path = pwd;

list = dir(path);

S = dir(fullfile(path, '*.csv'));

for k = 1:numel(S)

F = fullfile(S(k).folder,S(k).name);

opts = detectImportOptions(fullfile(S(k).folder,S(k).name),"VariableNamingRule","preserve",ImportErrorRule="omitrow",MissingRule="omitrow");

% There is no VariableName2 due to the omission of some file data among more than 100 files,

opts.SelectedVariableNames = {'VariableName1', 'VariableName2'};

% Error occurs because there is no VariableName2

opts.MissingRule = 'omitrow';

T = readtable(F,opts,"ReadVariableNames",true);

filename = getfield(S,{k},'name');

writematrix(filename,'naming.csv','Delimiter',',','QuoteStrings','all','WriteMode','append');

writematrix(matrix_data,'myData.csv','Delimiter',',','QuoteStrings','all','WriteMode','append');

end

Answer 1

[Aditya]

Hi 성 황,

To handle the issue of missing variables (e.g., VariableName2) when reading multiple files with 'detectImportOptions', you can add a check to ensure the variable exists before setting the 'SelectedVariableNames'. Additionally, you can skip the 25th file as requested.

Here is an updated version of your code:

path = pwd;
list = dir(path);
S = dir(fullfile(path, '*.csv')); 

for k = 1:numel(S)
    % Skip the 25th file
    if k == 25
        continue;
    end
    
    F = fullfile(S(k).folder, S(k).name);
    opts = detectImportOptions(F, "VariableNamingRule", "preserve", ...
                               "ImportErrorRule", "omitrow", "MissingRule", "omitrow");
    
    % Check if 'VariableName2' exists in the file
    if ismember('VariableName2', opts.VariableNames)
        opts.SelectedVariableNames = {'VariableName1', 'VariableName2'};
    else
        opts.SelectedVariableNames = {'VariableName1'};
    end

    % Read the table
    T = readtable(F, opts, "ReadVariableNames", true); 

    % Write the filename to 'naming.csv'
    filename = S(k).name;
    writematrix(filename, 'naming.csv', 'Delimiter', ',', 'QuoteStrings', 'all', 'WriteMode', 'append');
    
    % Write the table data to 'myData.csv'
    writematrix(T, 'myData.csv', 'Delimiter', ',', 'QuoteStrings', 'all', 'WriteMode', 'append');
end

I hope this helps!