How do I arrange folders before using HOG

Folder   = 'D:\Project\DB\train\';
FileList1 = dir(fullfile(Folder, '**', '*.tif'));
FileList = sort_nat( FileList1 );

Feature  = cell(1, numel(FileList));  % Pre-allocation
for iFile = 1:numel(FileList)
   File = fullfile(FileList(iFile).folder, FileList(iFile).name);
   Img  = imread(File);
   Img  = imresize(Img, [200, 50]);
   Feature{iFile} = hog_feature_vector(Img);
end
% Maybe:
Feat1 = cat(1, Feature{:});  % Or cat(2, ...) ?!
save('featurs_T.mat', 'Feat1');


Folder2   = 'D:\Project\DB\test\';
FileList22 = dir(fullfile(Folder2, '**', '*.tif'));
FileList2 = sort_nat( FileList22 );

Feature2  = cell(1, numel(FileList2));  % Pre-allocation
for iFile2 = 1:numel(FileList2)
   File2 = fullfile(FileList2(iFile2).folder, FileList2(iFile2).name);
   Img2  = imread(File2);
   Img2  = imresize(Img2, [200, 50]);
   Feature2{iFile2} = hog_feature_vector(Img2);
end
% Maybe:
Feat2 = cat(1, Feature2{:});  % Or cat(2, ...) ?!
save('featurs_S.mat', 'Feat2');

>> HOG_NEW

Error using regexprep

The 'STRING' input must be either a char row vector, a cell array of char row vectors, or a string

array.

Error in sort_nat (line 46)

c2 = regexprep(c,'\d+','0');

Error in HOG_NEW (line 7)

FileList = sort_nat( FileList1 );

>>