Extract rows separately from multiple files.

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C Smyth 2017-12-13

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https://ww2.mathworks.cn/matlabcentral/answers/372779-extract-rows-separately-from-multiple-files

评论： Jan 2017-12-14

I have 90 files each with three columns and about 2000 rows of data. I want to match/extract the first row in each of the files together, then the second, then the third and so on. Anyone know an efficient way of doing this? Thanks

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Jan 2017-12-13

It would be useful if you mention, in which format the files are written. It matters if they are MAT files, JPEG or text files.

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Answer 1

Jan 2017-12-13

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https://ww2.mathworks.cn/matlabcentral/answers/372779-extract-rows-separately-from-multiple-files#answer_296102

The most efficient way is to read all files into an array and sort the data as you want.

To get a more explicit answer, please explain what "match/extract the first row in each of the files together" means. Without knowing this detail, an answer must remain very vague.

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C Smyth 2017-12-14

Thank you for your reply! When I say match/extract, I want to input the first row of each file into an equation, then repeat the equation with the second row of each file and so on. But instead of re-writing the equation is there a way to automatically do this. All of the files are MAT files. I hope this makes more sense. Thank you

Jan 2017-12-14

在 MATLAB Online 中打开

Load all files in a loop:

Folder  = 'C:\Temp';  % Adjust this
DirList = dir(fullfile(Folder, '*.mat'));
nData   = numel(DirList);
Data    = cell(1, nData);
for k = 1:nData
  FileData = load(fullfile(Folder, DirList(k).name)); 
  Data{k}  = FileData;  % Or FileData.YourField, adjust this
end

Now you can process the data in a loop:

for kRow = 1:nRows
  Row = zeros(nData, ???);
  for kData = 1:nData
     Row(kData, :) = Data{kData}(kRow, :);
  end
  ... Do what you want with the Row data...
end