Read files in a specific order

Question

Isma_gp 2018-5-23

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编辑： Stephen23 2021-6-22

Hi, I have a series of files named with a date, for every third hour i.e. "NUM_1985_6_4_0_0.dat", "NUM_1985_6_4_3_0.dat", "NUM_1985_6_4_6_0.dat" ,....., "NUM_1985_6_4_21_0.dat",......, "NUM_1985_6_10_21_0.dat", "NUM_1985_6_11_0_0.dat". I'm using the dir command before using the fopen command. Is there any option when using the dir command to be able to list the files on a specific order. I would like to read the files by dates, however, the dir command gives me a list of files where the first one is "NUM_1985_6_10_0_0.dat" following a different logic, where the number 1 goes first in the list.

Thanks

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Answer 1

Stephen23 2018-5-23

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编辑：Stephen23 2021-4-18

在 MATLAB Online 中打开

Download my FEX submission natsorfiles, which was designed to fix the exact problem that you are having. Use it to simply sort the output from DIR:

D = '.'; % folder path
S = dir(fullfile(D,'*.dat'));
S = natsortfiles(S); % alphanumeric sort by filename
for k = 1:numel(S)
    F = fullfile(D,S(k).name)
    ... import/process file F
end

Here is natsortfiles used on your example filenames:

>> C = {'NUM_1985_6_4_0_0.dat';'NUM_1985_6_4_3_0.dat';'NUM_1985_6_4_6_0.dat';'NUM_1985_6_4_21_0.dat';'NUM_1985_6_10_21_0.dat';'NUM_1985_6_11_0_0.dat'};
>> C = C(randperm(numel(C))) % "random" order
C =
  NUM_1985_6_11_0_0.dat
  NUM_1985_6_4_0_0.dat
  NUM_1985_6_4_21_0.dat
  NUM_1985_6_4_3_0.dat
  NUM_1985_6_4_6_0.dat
  NUM_1985_6_10_21_0.dat
>> D = natsortfiles(C) % alphanumeric sort
D =
  NUM_1985_6_4_0_0.dat
  NUM_1985_6_4_3_0.dat
  NUM_1985_6_4_6_0.dat
  NUM_1985_6_4_21_0.dat
  NUM_1985_6_10_21_0.dat
  NUM_1985_6_11_0_0.dat

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Luke Riddell 2021-6-22

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Hi Stephen,

I've tried this but I get an error returning.

When using:

S = dir(fullfile(FinalFolderloc,'*.ASC'))
S = natsortfiles(S)

It returns the error in line with the natsortfiles function:

" Error using bsxfun

Non-singleton dimensions of the two input arrays must match each other.

Error in natsortfiles (line 231)

mat(logical(bsxfun(@eq,vec,nmn).')) = fnm; % TRANSPOSE bug loses type (R2013b)"

Do you have any advice?

Stephen23 2021-6-22

编辑：Stephen23 2021-6-22

@Luke Riddell: you seem to have found a bug in NATSORTFILES. I just uploaded a new version to FEX, please download it, try it, and let me know if it works as expected.

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Answer 2

Rik 2018-5-23

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You can sort the output or dir any way you like. See below for an example.

filelist=dir('NUM_*.dat');
dates=[filelist.datenum];
[~,order]=sort(dates);
filelist=filelist(order);

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Stephen23 2018-5-23

编辑：Stephen23 2018-5-23

This is a very fragile solution, because it assumes that the files themselves were written in the same order as the data was recorded: this will break easily, e.g. any time a file is edited, or if the files are copied from one folder to another.

"Can we sort the name field from dir?"

Yes. See my answer to know how.

Bin Qi 2021-2-4