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

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!

Answer 1

[Stephen23]

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

[Sam N]

Thank you so much!

Answer 2

[dpb]

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.

[Walter Roberson]

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);

result should be a non-scalar struct array with fields results and prep