MATLAB: Array from structs in a workspace

array of .mat files from workspace

Good day.

I’m a little bit mixt up with chars, doubles, operands, and so on…

1st. I’m loading a bunch of structs from directory to workspace.

files=dir('C:\...\*.mat');
for i=1:length(files)
    load(files(i).name);
end

I want to make from them an array.

array=[name1 name2 ... name118]

This method produces expected outcome – a struct 1×118. The only undesirable thing is to type all the 118 names “manually”.

I trade some “shortcuts”…

array = files;

Produces incorrect array 118×1 with some data about files, not their fields.

array =(files(i).name);

Asks to check for missing argument or incorrect argument data type in call to further function 'struct2cell'.

array =(1:files(i).name);

Error due to colon operator with char operands, first and last operands must be char.

Search in manuals and “ask” section is still in progress. Who – also can't fit, because at that point of the script are additional/not .mat variables (files and i) in workspace.

Maby someone has a hint on how I could avoid typing in “manual”?

Best Answer

projectdir = 'C:\...';
dinfo = dir( fullfile(projectdir, '*.mat') );
filenames = fullfile( {dinfo.folder}, {dinfo.name} );
for i = length(files) : -1 : 1
    array(1,i) = load(filenames{i});
end

The backwards loop is for efficiency, as it initializes the struct to full size and so does not need to keep extending the struct like you would if you looped forwards.

Related Solutions

MATLAB: How to save different mat files from different folders in a cell array

If the goal is to store each mat file in a separate cell with the data of the variables each of the mat files concatenated into one cell, refer to the code below:

projectdir = '.';   %or name of containing folder
foldinfo = dinfo(projectdir);
foldinfo(~[foldinfo.isfolder]) = [];  %get rid of non-folders
foldinfo(ismember({foldinfo.name}, {'.', '..'})) = [];  %get rid of . and .. folders
foldnames = fullfile(projectdir, {foldinfo.name});
numfold = length(foldnames);
out = cell(1275,1); % initialize the empty cell array.
for D = 1 : numfold
    thisfold = foldnames{D};
    dinfo = dir( fullfile(thisfold, '*.mat'));
    filenames = fullfile(thisfold, {dinfo.name});
    numfile = length(filenames);
    for F = 1 : numfile
        thisfile = filenames{F};
        file_struct = load(thisfile);
        %now extract variables from file_struct and process them
        for n = 1:numel(thisfile)
           out{(D-1)*25 + F,1} = cat(1,out{D*F},file_struct.(thisfile{n}));
        end
    end
end

MATLAB: Reading Netcdf in a loop

When you are using ** then the files will not be in projectdir, they will be in a subfolder of it. So you need to replace

filenames = fullfile( projectdir, {dinfo.name} );

with

filenames = fullfile( {dinfo.folder}, {dinfo.name} );

The folder field did not exist for older MATLAB, but those older MATLAB did not support ** subfolder searches either.

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