MATLAB: How to programmatically access specific variables that are dynamically loaded

assignmentdynamicdynamically loadedloadvariablevariable assignment

I am trying to load a specific variable and use it in my program. When I do so (using the following code), the data comes in as a struct (e.g. x.out1, x.out2, etc.)

x=load(strcat('Testfiles\', testcase.filename),strcat('out',num2str(num_videos)));

Because the content of x is dynamic, I cannot explicitly state which outN I am looking for in the code.

vid=x.out(...);

Because this is not a string, but a variable assignment, I cannot use strcat('out',num2str(num_videos)).

How can I assign the loaded variable to vid?

Thanks, Sean

Best Answer

Use fieldnames() to get your true variable names then use dynamic field name technique to get the value.

VarNames=fieldnames(x);
MyVarName=VarNames{1};
Value=x.(MyVarName)

Related Solutions

MATLAB: How to load saved workspace in a custom named variable

The efficient approach is to use indexing (rather than anti-pattern dynamic variable names):

https://www.mathworks.com/help/matlab/import_export/process-a-sequence-of-files.html

It is easy to import the file data into one cell array or one structure, e.g. the same one that dir returns:

D = 'absolute or relative path to the folder where the files are saved';
S = dir(fullfile(D,'*mat'));
for k = 1:numel(S)
    F = fullfile(D,S(k).name);
    S(k).data = load(F);
end

and then you can simply access the data from every file using basic and very efficient indexing, e.g. the third file:

S(3).name
S(3).data

If all of your .mat files contain variables with the same names (which is good data design) then you can also un-nest them by concatenating the data structures them into one non-scalar structure, e.g.:

out = [S.data]
out(3).someVariable
out(3).otherThing

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

MATLAB: How to programatically make workspace variable name same as the .mat file name loaded into Matlab

A much better approach than awful dynamic variable names is to use simple, efficient indexing, e.g.:

D = 'path to the directory where the files are saved';
S = dir(fullfile(D,'*.mat'));
for k = 1:numel(S)
    F = fullfile(D,S(k).name);
    C = struct2cell(load(F));
    S(k).data = C{1}; % assumes exactly ONE variable per file
end

All of the data will be stored in the structure S:

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

Best Answer

Related Solutions

MATLAB: How to load saved workspace in a custom named variable

MATLAB: How to programatically make workspace variable name same as the .mat file name loaded into Matlab

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