I need to read a specific column from 30 files in a folder (read the same column from each of them) and plot each column as a line. How can I go about it?

I have a bunch of files with columns of data, all saved to a folder that has only these files in it. I need to load the data from each of these files and then plot one of the columns of each file (the same column in each file), each column being a different line in the same plot. The name of the files, while similar, is different for each (they are all 'PowerMat_(array of parameters which is different for each file).mat).

I have created a code that will read one file, the column I need and plot it against an x axis that I chose. This code (linked below) will read the file from the workspace as I uploaded beforehand. But this is not what I want for the code I need to produce. I want it to read data from the directory itself as it would be too time consuming to upload each file onto the workspace as eventually I will be working with hundreds of files. Therefore I need to create a for loop to read and plot all of these files at once, and I am struggling to find the correct way of doing this.

Thank you.

x = 15 : 1 : 50 ;           %Array of z values on zmin_15 (from 15 to 50 in steps of 1)
R = 30                      %Number of runs of the simulation
n = 39 ;                    %Nº of column to read of the PowerMat (each column is wavevector value)
y = PowerMat_1 (: , n) ;    %Selecting column n on file
figure ;                    %Open separate figure window
plot (x , y) ;              %Plot for exampleSim
set(gca, 'YScale', 'log')   %Sets y axis to be logarithmic scale. Comment for linear
title('Power Spectrum vs Redshift at k=') ;
xlabel('Redshift (Z)') ;
ylabel('Power Spectrum') ;

[dpb]

See example of a datastore at <<Read-a-sequence-or-collection-of-text-files>

Answer 1

[Mathieu NOE]

hello Agustina

see code below :

% use the structure returned by DIR:
P = cd; % working directory 
S = dir(fullfile(P, 'PowerMat_*.mat'));
S = natsortfiles(S); % sort folders / file names into natural order 
                    % (download FEX : https://fr.mathworks.com/matlabcentral/fileexchange/47434-natural-order-filename-sort)
% init main code
x = 15 : 1 : 50 ;           %Array of z values on zmin_15 (from 15 to 50 in steps of 1)
R = 30 ;                     %Number of runs of the simulation
n = 39 ;                    %Nº of column to read of the PowerMat (each column is wavevector value)
figure(1) ; hold on

for k = 1:numel(S)
    fn = S(k).name;   % filename :  used for legend
    fn = strrep(fn,'_',' ');% replace _ by space for better legend rendering 
    leg{k} = fn;  % store in cell array
    
    % load data 
    F = fullfile(S(k).folder, S(k).name);
    data = load(F); % is structure
    names = fieldnames(data); % get fieldnames
    y = data.(names{1});  % your data (assumed in first fieldname)
    y = y(:,n) ;    %Selecting column n on data
    plot(x,y)
    
end
legend(leg); % put legend
hold off

[Agustina Magarinos-Rodriguez]

I will give that a go. Thank you!