How to load all the data in one folder

Question

Sikai Wu 2021-2-19

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/750104-how-to-load-all-the-data-in-one-folder

编辑： Stephen23 2021-2-19

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.

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Sikai Wu 2021-2-19

在 MATLAB Online 中打开

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 2021-2-19

编辑：Stephen23 2021-2-19

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

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Answer 1

Stephen23 2021-2-19

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/750104-how-to-load-all-the-data-in-one-folder#answer_627694

编辑：Stephen23 2021-2-19

在 MATLAB Online 中打开

"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