How to add a column for data in datastore

Question

Saif Aljanahi 2021-3-27

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https://ww2.mathworks.cn/matlabcentral/answers/785136-how-to-add-a-column-for-data-in-datastore

回答： Khushboo 2022-11-4

I have a data store that holds 2,700 files, theses files are activities such (standing, walking, lying,...and etc).

the datastore contains all these files, all files having 3 columns (acceleration of x,y,z).

I want to write a code that can add a fourth column to this datastore depends on the original file name that I have added earlier to this datastore.

I want to do this, to make labeling and prepare my data for classification.

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Anup Thapa 2022-10-31

Hi. I have the same issue/need. What solution worked for you in the end?

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Answer 1

Khushboo 2022-11-4

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Hello,

As datastore simply reads the data from a file to a table, you will have to write the modified table back to the datastore. This can be done using something like this:

while hasdata(currentDs)
    [T, info] = read(currentDs);
    % Add a new column to the end of the table
    T.newCol = newColumnToBeAdded; %ensure that it is a cell array
    %Write the new modified file back the table
    filename = ['newfolder/modifiedfile_', num2str(info.Offset), '.csv']; 
    writetable(T, filename);
end
newDs = datastore('newfolder/*.csv');