Use fprintf name of array within the script

I am trying to find the sizes of many arrays, named "d25a%d" for %d values of 16:1:20. I'm using a for loop with f equal to these values, the first line is forming the name of the file "file = 'd25a%d'; File = sprintf(file,f);" and then finding the size for the array with the same name as File, in the form of "[a,z] = size(File);" and the result is the size of the character array.

How can this be fixed?

[Stephen23]

"How can this be fixed?"

By not forcing meta-data into variable names.

You forgot to tell us the most important information: how did those variables get into the workspace? I doubt that you wrote all of those variable names out by hand.... e.g. if you used LOAD, then that would be the place to fix your code:

S = load(..);

Answer 1

[Jan]

The main problem is to have a bunch of variables with an index hidden in the name. Don't do this. Store the data in an array. Then it is trivial to run a loop to get the sizes.

See: https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

[Sam Hurrell]

I'm aware of this issue and later in the script resolves this. However indexing the variables at this stage is necessary and cannot easily be altered.

[Jan]

If you have a complicated representation, which requires even more complicated methods to process them, do not imporve these methods, but the representation of the data. Of course you can convert the data to an array and use standard indices:

Array = {d25a16, d25a17, d25a18, d25a19, d25a20};

Why do you use the term "file"? Do you have to import data from files at first?

Answer 2

[Image Analyst]

Don't worry - it's not at all uncommon to have parameters encoded into the file names. It appears you're trying to create 5 file names, from d25a16.* to d25a20.*, and read in their contents into variables. You can use the FAQ to read them in

https://matlab.fandom.com/wiki/FAQ#How_can_I_process_a_sequence_of_files?

or try this code (untested):

for k = 16 : 20
    % Create filename.
    baseFileName = sprintf('d25a%d.dat', k);
    fullFileName = fullfile(folder, baseFileName);
    % If the file exists, read it in.
    if isfile(fullFileName)
        % Read in the matrix and get its size.
        data = readmatrix(fullFileName);
        [rows, columns] = size(data);
        fprintf('%s has %d rows and %d columns.\n', baseFileName, rows, columns);
    else
        % File does not exist.
        warningMessage = sprintf('File not found:\n   %s', fullFileName);
        fprintf('%s\n', warningMessage);
        uiwait(warndlg(warningMessage));
    end
end

If you simply have 5 matrices in your program and want their sizes, simply use size():

[rows(1), columns(1)] = size(d25a16);
[rows(2), columns(2)] = size(d25a17);
[rows(3), columns(3)] = size(d25a18);
[rows(4), columns(4)] = size(d25a19);
[rows(5), columns(5)] = size(d25a20);