How to load all the data in one folder

Path = 'D:\50-350\';
File = dir( fullfile(Path,'*.dat'));
FileNames = {File.name}';
Length_Names = size(FileNames,1);
for i=1:Length_Names
    filename=strcat(Path, FileNames(i));
    eval(['Data',num2str(i),'=','load(filename{1,1})',';']);
end

I have 3 targets here:

1、Find out all the files with '.dat' in folder '50-350';

2、Read the data;

2、Rename the data from ‘Data1 Data2 Data3 Data4...’ one by one;

By the codes above, I successfuly achieve the goals, but I find that the size of the data change.

For example: I load the ' 31.dat ' by the above codes, and rename it as ' Data31'. The size of Data31 is 3353×10 . If I read '31.dat' directly, the size is 2501×10. I am wonder why it happened.

[Sikai Wu]

for i=1:Length_Names
%     filename=strcat(Path, FileNames(i));
%     eval(['Data',num2str(i),'=','load(filename{1,1})',';']);
    filename=[num2str(i),'.dat'];
    chr=[Path filename];
    Data{i}=load(chr);
end

I change the code as above. It seems goos. I am not sure whether it is correct.

[Stephen23]

For robustness you should preallocate Data before the loop.

Also fullfile is recommended instead of string concatenation.

You will probably find that the files are not imported in numeric order: to get numeric order based on numbered filenames (without leading zeros, as your example shows) you will need to do either of these:

• sort the names alphanumerically.
• generate the filenames (rather than using DIR), as shown here:

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

Answer 1

[Stephen23]

"I am wonder why it happened."

Because you always load exactly the same file data (note the indexing you used):

filename{1,1}

Your code always loads the first file and ignores all the other files.

In any case your approach is not robust. Here is a simpler and more robust way to import that data:

P = 'D:\50-350\';
S = dir(fullfile(P,'*.dat'));
for k = 1:numel(S)
    F = dir(fullfile(P,S(k).name));
    S(k).data = readmatrix(F); % much better than EVAL and LOAD.
end

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

Depending on how the files are named, you might also find this useful:

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

[Sikai Wu]

Thanks for you help. My software is 2017a. 'readmatrix' is expanded in 2019a.

[Stephen23]

For 2017a you can try dlmread or cvsread or textscan or whatever suits your file format.