Import N excel files in N matrix, with name in function of a variable

I have a large number of excel file with the name like: NAME.000i000.csv where i is a variable, from 0 to N.

to import a single file I use this line of code and perfectly work

DATA1 = readtable("DIR\NAME.0001000.csv", opts);

How can I import all the N file and create N matrix with the name DATAi?

I have tried something similar to:

for i=1:N

eval(['DATA' num2str(i) '= i'])=readtable(""DIR\NAME.000%s000.csv",i, opts);

end

but it didn't work.

Thank you for your help

[Stephen23]

https://www.mathworks.com/matlabcentral/discussions/tips/849901-tutorial-why-variables-should-not-be-named-dynamically-eval

Rather than awkwardly forcing pseudo-indices into variable names (and making your data harder to work with) the much better approach is to use actual indexing into one array, for example:

C = cell(1,N);
for k = 1:N
    fnm  = ..
    C{k} = readtable(fnm,opts);
end

Using indexing is more efficient, more robust, easier to work with, less buggy, and easier to debug.

Using indexing is exactly what the MATLAB documentation recommends:

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

[Andrea]

Thank you for your answer. this method worked too

Answer 1

[Hitesh]

Hi Andrea,

You need to use structure within the loop to dynamically create variables for each corresponding CSV file when importing multiple CSV files in MATLAB. However, using "eval" for creating variable names dynamically is generally discouraged due to potential issues with code readability and debugging.

For more information on " Why Variables Should Not Be Named Dynamically (eval)", refer to the following link:

https://www.mathworks.com/matlabcentral/discussions/tips/849901-tutorial-why-variables-should-not-be-named-dynamically-eval

Refer the following code for achieving same using structure:

N = 10; % Replace with your actual number of files 
DATA = struct(); % Initialize an empty structure 
for i = 1:N 
    fileName = sprintf('DIR\NAME.000%d000.csv', i); 
    DATA.(sprintf('DATA%d', i)) = readtable(fileName); 
end 

[Andrea]

Thank you. it worked fine

Answer 2

[埃博拉酱]

DATA=arrayfun(@(Filename)readtable(Filename,opts),compose("DIR\NAME.000%u000.csv",1:N),UniformOutput=false);
%If you insist on creating a series of workspace variables called DATAi despite the dissuasion of others:
arrayfun(@eval,compose("DATA%u=Data{%u};",1:N));

[Stephen23]

"...despite the dissuasion of others"

and also despite the dissuasion of the MATLAB documentation, which states "A frequent use of the eval function is to create sets of variables such as A1, A2, ..., An, but this approach does not use the array processing power of MATLAB and is not recommended. The preferred method is to store related data in a single array".

source: https://www.mathworks.com/help/matlab/matlab_prog/string-evaluation.html