How to automatically import multiple column vectors into Matlab from multiple .csv files using Live Script and a For Loop?

Hello, I'm a coding and generally computing aliterate. I've used Matlab to evaluate data for my experiments in the University and now I'm also using it at work. Normally I get a large set of .csv files which I can individually import into Matlab. Today I found a tool "Import Data" and I've been experimenting with it, but I can't find a way to "add" into the Live Script a "For Loop code" so that the Files will automatically be read one by one storing my data into column vectors (arrays) with the same name but different numbers. Example: Pol_X_W, Pol_X_I, where X can be 000, 005, 010, 015... and so on. And also reading it from the same files by those arbitraty X numbers. I have no clue how a computer works, so I really would need you to explain to me either how the computer itself processes that information, so that I can find extra information on that on the web and then figure out a coding method or maybe theres a generic solution I haven't tried out. More specifically I just need the computer to understand that X is a variable that has to run throu a list of numbers I want to choose within the "Live Script" of the Data Import Tool.

Here is what the Code looks like:

Set up the Import Options and import the data

opts = delimitedTextImportOptions("NumVariables", 2);

% Specify range and delimiter

opts.DataLines = [2, Inf];

opts.Delimiter = ",";

% Specify column names and types

opts.VariableNames = ["Pol_20_W", "Pol_20_I"];

opts.VariableTypes = ["double", "double"];

% Specify file level properties

opts.ExtraColumnsRule = "ignore";

opts.EmptyLineRule = "read";

% Import the data

tbl = readtable("/Users/User/Downl/Po/Spectrum_pol_020.csv", opts);

Convert to output type

Pol_20_W = tbl.Pol_20_W;

Pol_20_I = tbl.Pol_20_I;

Clear temporary variables

clear opts tbl

The 20 could be 020 I don't mind, but I would like to put 'X' and make a list of all the posible X values and automatically go throu them... cuz they are like 80 files... Thank you so much for reading this.

[Benjamin Thompson]

Can you post sample CSV files and more information about what kind of output you want?

[Manuel Rodrigo Lomas Anza]

The CSV files are like two colomns each with a title and then a set of 1340 rows. so they are like two 1341x2 matrices. And the Output I was looking for was separate column vectors. Like 1340x1 colomuns. But if you know how to manage these files in 1340x80 choosing arbitrarily which column goes to what matrix/tbl... that would be dope too.

Answer 1

[Highphi]

here ya go:

opts = delimitedTextImportOptions("NumVariables", 2);
% Specify range and delimiter
opts.DataLines = [2, Inf];
opts.Delimiter = ",";
% Specify column names and types
% opts.VariableNames = ["Pol_20_W", "Pol_20_I"]; leave this out for now
opts.VariableTypes = ["double", "double"];
% Specify file level properties
opts.ExtraColumnsRule = "ignore";
opts.EmptyLineRule = "read";

for i = 1:80 % or whatever number, just follow the logic below
    
    myNumber = num2str(i); % convert number to string
    if length(myNumber) == 1
        myNumber = ['0', myNumber]; % if less than 10 -> if you go over 100 this needs to be tweaked
    end
    
    varName1 = ['Pol_', myNumber, '_W'];
    varName2 = ['Pol_', myNumber, '_I'];
    opts.VariableNames = [varName1, varName2]; % NOW we use it
    
    csvFilename = ['/Users/User/Downl/Po/Spectrum_pol_0', myNumber, '.csv'];

    tbl = readtable(csvFilename, opts);
    
    eval(['values_W = tbl.', varName1, ';'];
    eval(['values_I = tbl.', varName2, ';'];

    % ^ do all of that inside the for loop, going through all files
    
    % then do something with values_W & values_I
    % check out the table2array function for more user friendly matrices
end

clear opts

[Manuel Rodrigo Lomas Anza]

Hi! I called the function "Respuesta.m".

I thought it would work, but I tried to run it and it said this.

"Error using Respuesta (line 26)

Unrecognized table variable name 'Pol_0_W'."

The program is creating a table 1340x1 instead of 1340x2, with each a column name. I guess that's the problem, but idk why. And in the table the column is named "Pol_0_WPol_0_I".

Besides that there are two ")". Thank you so much for the help. If you got time and know a fix for this I would appriciate it if you could give me a hint.

[Highphi]

of course!

hm, Pol_#_W it should never be 0 because we're starting at i = 0

but I also see that the evals forgot the ')' at the end (easy fix)

do you think you could give me a sample file of the data so I can actually import it? that would help me fully solve this :)