MATLAB: How to use who within eval

eval

Here is the code:

file_name = 'test';
eval(['file_length = length(who(''-file'',' file_name '));']);

But this doesn't work, because who requires a quoted string as a variable. Then I tried this,

eval(['file_length = length(who(''-file'', ''file_name'' ));']);

It didn't work, apparently. Now file_name showed up instead of the value I put in it. This sounds a very simple question, but I just don't know what to do. Help!

Best Answer

This is a working example:

clear
x = zeros(10,1); y = x;
save matlab.mat
file_name='matlab.mat';
eval('file_length = length(who(''-file'',file_name))')
file_length =
     2

EDIT: Although I answered the question you asked, I agree with Sean and the Cyclist that it would be better not to use eval. See Loren's blog for some reasons.

Related Solutions

MATLAB: How to prevent MATLAB from running out of memory when running a large number of functions with EVAL that generate a large amount of data in MATLAB 7.8 (R2009a)

To prevent a memory leak in such a situation, use 'clear functions' periodically in your code. This is necessary since MATLAB stores some information about MATLAB files and calling 'clear functions' clears up this memory space.

For example, you can modify the previous code example as follows:

%%test_loading.m
num_files = 900;
for loops = 1:num_files
      if loops >= 2
          old_file = ['test_data',num2str(loops-1),'.m'];
          new_file = ['test_data',num2str(loops),'.m'];
          copyfile(old_file,new_file);
      end
      file_name = ['test_data',num2str(loops),'.m'];
      name_length = length(file_name);
      eval(file_name(1:name_length-2));
      disp(['Analyzing ',file_name]);
      if loops > 3,
          delete(old_file);
      end    
      clear functions;
end

MATLAB: Trouble with code to check for Excel file existence

if exist(file_name,'file') == 0

Best Answer

Related Solutions

MATLAB: How to prevent MATLAB from running out of memory when running a large number of functions with EVAL that generate a large amount of data in MATLAB 7.8 (R2009a)

MATLAB: Trouble with code to check for Excel file existence

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