read mat files with specific and dynamic name format and import data

Question

Sam N 2021-7-5

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https://ww2.mathworks.cn/matlabcentral/answers/872543-read-mat-files-with-specific-and-dynamic-name-format-and-import-data

评论： Sam N 2021-7-6

matFiles = dir('s*_results.mat');
for k = 1:length(matFiles)
    rawdata = fullfile(matFiles, k);
    filename = importdata(rawdata);
end
    myVars = {'results', 'prep'};
    filedata = load(filename, myVars{:});

I'm trying to read all the files with names such as "s001_results.mat", "s002_results.mat" and so forth until "s150_results.mat" which are mat files with more than the two variables (results and prep) that I need. Essentially, I need to read the results and prep variables in all 150 of these mat files but I keep getting the error that the file cannot be imported using the importdata function. Please help!

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Answer 1

Stephen23 2021-7-6

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https://ww2.mathworks.cn/matlabcentral/answers/872543-read-mat-files-with-specific-and-dynamic-name-format-and-import-data#answer_740713

编辑：Stephen23 2021-7-6

在 MATLAB Online 中打开

The best approach is to use the same structure as DIR returns. This has the benefit that the filenames and filedata are automatically and correctly collated together. For example:

P = 'absolute or relative path to where the files are saved'
S = dir(fullfile(P,'s*_results.mat'));
for k = 1:numel(S)
    F = fullfile(P,S(k.name));
    T = load(S); % you can optionally specify the variable names here.
    S(k).prep    = T.prep;
    S(k).results = T.results;
end

And that is all! You can trivially access the filenames and filedata, e.g. for the second file:

S(2).name
S(2).prep
S(2).results

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

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Sam N 2021-7-6

Thank you so much!

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Answer 2

dpb 2021-7-5

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https://ww2.mathworks.cn/matlabcentral/answers/872543-read-mat-files-with-specific-and-dynamic-name-format-and-import-data#answer_740568

编辑：dpb 2021-7-6

在 MATLAB Online 中打开

matFiles = dir('s*_results.mat');
myVars = {'results', 'prep'};
varsList=char(join(myVars));
for k = 1:length(matFiles)
  load(matFiles(i).name, varsList);  
end
...

The list of variables to load must be char() vector of names comma-separated or just a single name (which could include wildcards, but that doesn't work here).

See the doc for load for details on syntax.

ADDENDUM:

Your syntax results in a list, not a string and (I think) the comma delimter is requred, anyways...

>>  myVars = {'results', 'prep'};
myVars{:} 
ans =
    'results'
ans =
    'prep'
>> 

whereas

>> char(join(myVars,','))
ans =
    'results,prep'
>> 

is the requisite char string list of variables to mimic what would type at command line interactively. I didn't test if load has been update to handle the new string class.

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Walter Roberson 2021-7-6

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No join!

matFiles = dir('s*_results.mat');
nfiles = length(matFiles);
myVars = {'results', 'prep'};
data_cell = cell(nfiles, 1);
for k = 1:length(matFiles)
  data_cell{k} = load(matFiles(i).name, myVars{:});
end
data_struct = cell2mat(data_cell);