Read multiple CSV files from different folders uing readtable

Hello

I have to read multiple csv files from differnt folders on the same editor window to plot on the same figure.

I have tried sth like this

ds1 = datastore('*.csv');

T = readall(ds1);

buit this gives data for only the currecnt directory.

I have file paths p1 , p2 and p3 for each 3 folders and i want to read thoese files from the 3 folder,

I am stuck and appreciate your help

Thank you

Answer 1

[Image Analyst]

See the FAQ:

https://matlab.fandom.com/wiki/FAQ#How_can_I_process_a_sequence_of_files?

% Specify the folder where the files live.
myFolder = 'C:\Users\yourUserName\Documents\My CSV Files';
% Check to make sure that folder actually exists.  Warn user if it doesn't.
if ~isfolder(myFolder)
    errorMessage = sprintf('Error: The following folder does not exist:\n%s\nPlease specify a new folder.', myFolder);
    uiwait(warndlg(errorMessage));
    myFolder = uigetdir(); % Ask for a new one.
    if myFolder == 0
        % User clicked Cancel
        return;
    end
end
% Get a list of all files in the folder, and its subfolders, with the desired file name pattern.
filePattern = fullfile(myFolder, '**/*.csv'); % Change to whatever pattern you need.
theFiles = dir(filePattern);
for k = 1 : length(theFiles)
    baseFileName = theFiles(k).name;
    fullFileName = fullfile(theFiles(k).folder, baseFileName);
    fprintf(1, 'Now reading %s\n', fullFileName);
    % Now do whatever you want with this file name,
    % such as reading it in as a table.
    thisTable = readtable(fullFileName);
end

[Image Analyst]

Because you left the semicolon off, that should print out the values of B to the command window. Do you not see them?

If you want to store/save them for later, you'll have to make B a matrix and give the column number, like

B(:, k) = data(:, 3); % Store 3rd column of data in k'th column of B.

Answer 2

[KSSV]

thepaths = {p1,p2,p3} ;
for i = 1:3 % loop for ech folder 
    csvFiles = dir([thepaths{i},'\*csv']) ;  % get ll csv files in the folder 
    N = length(csvFiles) ; 
    for j = 1:N  % loop for each csv file 
        csvFile = fullfile(csvFiles(j).folder,csvFiles(j).name) ;
        T = readtable(csvFile) ;
        % do what you want 
    end
end

[KSSV]

Check the paths......

[Stephen23]

"I am getting only the last iteration"

If you want to store the data from every iteration then you will need to allocate that data to an array, just as the MATLAB documentaton shows:

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

https://www.mathworks.com/help/matlab/matlab_prog/access-data-in-a-cell-array.html

Answer 3

[Image Analyst]

You need to index f. Actually I'd use more descriptive variable names. No one wants to look at code that looks like aphabet soup.

% Get a list of all files in the folder with the desired file name pattern.
filePattern = fullfile(myFolder, '*.CSV'); % Change to whatever pattern you need.
fileList = dir(filePattern);
for k = 1 : length(fileList)
    % Read in this table.
    baseFileName = fileList(k).name;
    fullFileName = fullfile(fileList(k).folder, baseFileName);
    thisTable = readtable(fullFileName); 
    % Extract the third column only.
    column3 = thisTable{:, 3};
    % Append this column to our master vector.
    if k == 1
        allColumn3s = column3;
    else
        allColumn3s = [allColumn3s; column3]
    end
end
numBins = 4;
histogram(allColumn3s, numBins)
grid on;

If you have any more questions, then attach your data (at least 2 CSV files) with the paperclip icon after you read this:

TUTORIAL: How to ask a question (on Answers) and get a fast answer

[Image Analyst]

Then can you please click the "Accept this answer" link? Thanks in advance. 😃