How to read all .csv files from a folder in an order?

My programme is not reading the files in a proper order. The order of the files is sky_0, sky_1, sky_2,... sky_2001.

But it is reading in the order sky_0, sky_1, sky_10, sky_1000, sky_1001,... sky_1009, sky_10,...

Can anybody help me to read it in the right order?

[Stephen23]

https://web.archive.org/web/20201205132552/https://www.mathworks.com/matlabcentral/answers/678103-how-to-read-all-csv-files-from-a-folder-in-an-order

Answer 1

[Walter Roberson]

https://www.mathworks.com/matlabcentral/fileexchange/47434-natural-order-filename-sort

[Sateesh Kandukuri]

Sorry, sir, I am getting this error.

Unrecognized function or variable 'natsortfiles'.

Error in Readfiles (line 4)

N = natsortfiles({S.name});

[Rik]

How did you try to add the function to Matlab?

If you're using R2017b or newer you can use the Add-On Manager to add this function to Matlab.

[Stephen23]

"Sorry, sir, I am getting this error. "

Did you click the big blue "Download" button and unzip it into a folder on the MATLAB path (e.g. the current directory)?

[Sateesh Kandukuri]

I added this function. But now I am getting this error.

Dot indexing is not supported for variables of this type.

Error in Readfiles (line 11)

data = readmatrix(fnames(idx).name);

[Sateesh Kandukuri]

I attached the code for your reference.

[Stephen23]

I doubt that you would get that error with that code: the variable FNAMES is the structure returned by DIR, so that code shows no reason for that error. If you want to use NATSORTFILES to sort the filenames then its output is a cell array (just as its documentation clearly states) so you would then have to use curly braces to access the filenames:

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

Or you could use the second output to sort the structure itself, whatever works best for you.

The NATSORTFILES documentation has plenty of examples, incuding several using the output of DIR.

[Sateesh Kandukuri]

Dear Stephen Cobeldick, still, I am getting the error. Could you please help me out. I am attaching the code for your reference.

[Walter Roberson]

D = 'D:\Sateesh\CoPd\T14.out';
S = dir(fullfile(D,'*.csv'));
N = natsortfiles({S.name});
% Pre-allocate output vector
ranges = zeros(numel(N), 1);
% Loop over file names
for idx = 1:numel(N)
    % Read the CSV data
     data = readmatrix( fullfile(D, N{idx}) );
    % Get the 5th column
    col5 = data(:,5);
    % Get the range for this file
    ranges(idx) = max(col5) - min(col5);
end
% Write the result
endt=(1e-11)*numel(N);DD, 
t=1e-11:1e-11:endt;
ranges1=[t' ranges];
writematrix(ranges1, 'ranges.csv');
plot(t',ranges)

[Sateesh Kandukuri]

Dear Walter Roberson, I am getting the error, Unrecognized function or variable 'DD'.

Error in Readfiles2 (line 16)

endt=(1e-11)*numel({N});DD,

I have tried without and with D; but, I am getting the following error.

Error using horzcat

Dimensions of arrays being concatenated are not consistent.

Error in Readfiles2 (line 18)

ranges1=[t' ranges];

[Walter Roberson]

I have no idea what you put that DD into the code. I would suggest the lines should be

t = 1e-11 * (1:numel(N));

and remove the line

endt=(1e-11)*numel(N);DD, 

[Sateesh Kandukuri]

Dear Walter Roberson, thank you so much for the help. It is working.

[Sateesh Kandukuri]

Dear Walter Roberson, I ran the same programme to similar files in another folder. But, I am getting an error.

Index in position 2 exceeds array bounds (must not exceed 2).

Error in Readfiles2 (line 12)

col5 = data(:,5);

Could you please help me out

[Walter Roberson]

One of your files doesn't have 5 columns

When the program stops look at N{idx} for the name of the problem file

[Sateesh Kandukuri]

Thank you sir, I resolved the problem.