how to write a script that outerjoins multiple data files

Question

alpedhuez 2019-4-10

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/455583-how-to-write-a-script-that-outerjoins-multiple-data-files

评论： alpedhuez 2019-4-10

I have files "File1.csv", "File2.csv",.... and "File33.csv". Each of 33 files has a key variable 'date'. I would need to outerjoin these 33 files using 'date' as the key variable. I understand it is a generalization of

B=outerjoin(File1,File2,'Keys', 'date', 'MergeKeys', true)

But I need to understand

(1) how to write a loop to read 33 files from C:\Dropbox (say)

(2) how to write a loop to outerjoin 33 files

(3) how to write a script to save the output file into C:\Dropbox

I will appreciate a code sample.

Thank you.

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Answer 1

Guillaume 2019-4-10

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/455583-how-to-write-a-script-that-outerjoins-multiple-data-files#answer_370040

在 MATLAB Online 中打开

Something like (untested, expect typos):

folder = 'C:\dropbox';
filelist = dir(fullfile(folder, 'File*.csv'));
for fileidx = 1:numel(filelist)
    filecontent = readtable(fullfile(folder, filelist(fileidx).Name));
    if fileidx == 1
        joined = filecontent;
    else
        joined = outerjoin(joined, filecontent, 'Keys', 'Date', 'MergeKeys', true)
    end
end
writetable(joined, fullfile(folder, 'joined.csv'));