Do calculations in csv data one csv file at the time

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Martin Kneyber 2024-4-27

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编辑： Voss 2024-4-28

I have several csv files. Want to perform calculations on the data in the csv file, for example calculating variable x. Then, I want one table with in the first column the filename of each csv file and then in the next column the calculated variable x. How can I do this? Newbie,so sorry for asking.

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Martin Kneyber 2024-4-27

Sure, but there are a lot of files and each files has a big number of rows - hence looking for a way to automate it

Dyuman Joshi 2024-4-27

See - https://in.mathworks.com/help/matlab/import_export/process-a-sequence-of-files.html

Use readtable or readmatrix to import the data, and their counter-parts writetable or writematrix to export the data.

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Answer 1

Voss 2024-4-27

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Something like this; adjust as necessary.

% use dir() to get info about the relevant csv files:
csv_dir = '.';
F = dir(fullfile(csv_dir,'*.csv'));
filename = fullfile({F.folder},{F.name}).';
% preallocate x. I assume it's a scalar numeric for each file
N = numel(F);
x = zeros(N,1);
% loop over the files
for ii = 1:N
    
    % read each file (use the appropriate function with the appropriate options)
    data = readtable(filename{ii});
    
    % ...
    % calculate this_x based on data
    % ...
    
    % store this_x
    x(ii) = this_x;
    
end
% write file with file names and x values
T = table(filename,x);
writetable(T,'out.csv')