Assign variables while importing data

I have a data set with multiples files, and there are 2 coloumns in each file. I have imported the files using the following code:

  files = dir('*.txt');
for i=1:length(files)
    eval(['load ' files(i).name ' -ascii']);
    
end

I have the data in my workspace now but I need to assign variables to each coloumn. Furthermore, I have to use those variables in a function to normalize all the data at the same time and plot in a single graph.

Is there any approach I can take to assign variables so that the code goes through each file one by one, and take the assigned variables to give answer for all dataset at once.

function [zero,norm,ramanzeronorm] = zeronorm(wavenumber,rm)

My variables are wavenumber and rm.

Any help will be appreciated.

Answer 1

[Stephen23]

Do NOT use eval for importing data, unless you intentionally want to force yourself into writing slow, complex, buggy code. Read this to know why:

https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

Instead you should import the data into a matrix, optionally assigning it to one array using indexing, for example using a cell array as the documentation examples show:

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

Or using the same structure returned by dir:

S = dir('*.txt');
for k = 1:numel(S)
    M = dlmread(S(k).name); % better than LOAD.
    ... do whatever with matrix M, e.g.:
        wn = M(:,1); % wavenumber
        rn = M(:,2); % rn
    ...
    S(k).data = M; % optional: store any data you want for later.
end

Then you can trivially access the data in that structure, e.g. using loops or indexing:

https://www.mathworks.com/help/matlab/matlab_prog/access-multiple-elements-of-a-nonscalar-struct-array.html

For example, you can easily vertically concatenate all of the file data together:

alldata = vertcat(S.data);

[ahmi ali]

Thanks a lot for your help!

Is there a way to extract data from struct and add it to the matrix M ? I want to plot the data from the struct into a single graph, so I want that the function is applied simultaneously on all data. That means the Matrix M has e.g 1024*5 , 5 coloumns in total. I hope I made the question clear enough.

[Stephen23]

You can store any data you want in the structure, e.g.:

for ...
    ...
    S(k).mycolumn = whatever column of data you want to store;
end
mymat = [S.mycolumn];

What size mymat is depends entirely on how often the loop iterates and on the size of each column: if each column you store has size 1024x1 and it iterates five times, then mymat will have size 1024x5.

Read more about how this works:

https://www.mathworks.com/help/matlab/matlab_prog/comma-separated-lists.html

https://www.mathworks.com/matlabcentral/answers/320713-how-to-operate-on-comma-separated-lists