How to use eval() command to save the workspace variables in different working directory?

The following code works fine in my GUI

Workspace variable : i=1; simtype='gopi'; t=[0 1]; e='hi';

eval(['save Batch_' num2str(i) '_Results_' simtype '.mat t;']); % storing of 't' variable in pwd

eval(['save Batch_' num2str(i) '_Results_' simtype '.mat ' e ' -append;']); % storing of some variables in pwd

eval (['Rin=load(''Batch_' num2str(i) '_Results_PE15.mat'');']); % load again the same variables from pwd

The above code used to save my workspace variables in present working directory. But i would like to save those workspace variables in different working directory. I have tried some comments but it doesnot work good, it shows error. Please check those codes below:

Error comes while using following codes:

%% pwds - different working directory - D:\matlabfiles\ACTIVITY\Itr 3\Script
eval(['save(fullfile(' pwds 'Batch_' num2str(i) '_Results_' simtype '.mat,t;']);

I am getting follwing error only when i am trying to save the file in different working directory (used above code).

% Error: Invalid use of operator

Kindly help me to get the correct code format for saving the workspace variables(not all variables - only some variables) in different working directory which also works in loops, if possible write through eval command itself.

[Stephen23]

"How to use eval() command to save the workspace variables in different working directory?"

Your task can be resolved much easier and much more efficiently using basic function syntax (just like the save documentation states) instead of command syntax that you used:

https://www.mathworks.com/help/matlab/matlab_prog/command-vs-function-syntax.html

Your inefficient, indirect approach using eval:

eval(['save Batch_' num2str(i) '_Results_' simtype '.mat t;']);

The simpler and more efficient approach:

save(['Batch_',num2str(i),'_Results_',simtype,'.mat'],'t')

Or even better with sprintf:

fnm = sprintf('Batch_%d_Results_%s.mat',i,simtype);
save(fnm,'t')

Now is a good time to learn the difference.

Answer 1

[Image Analyst]

Do not use eval. It is not needed - it's virtually never needed. Just use the commands themselves without wrapping them inside eval():

% Use a different folder ("D:\matlabfiles\ACTIVITY\Itr 3\Script") than the current working directory.
folder =  'D:\matlabfiles\ACTIVITY\Itr 3\Script' % Specify folder.
baseFileName = sprintf('Batch_%d_Results_%s.mat', i, simtype); % Specify the base file name.
% Construct the full file name.
fullFileName = fullfile(folder, baseFileName);
% Save to a .mat file.
save(fullFileName, 't');

[Gopinath Karuppannan]

Hi

Thanks for your quick response.

And it works good. i can able to save those files.

And just for understanding: Can we able to use eval() command to achieve this same working? - as workspace files to be stored in different working directory.

Thanks in advance

[Stephen23]

"Can we able to use eval() command to achieve this same working? - as workspace files to be stored in different working directory."

Why do you need eval to do that?

Every MATLAB user can simply write files to any directory by using absolute/relative filenames and the function form of some file exporting command. So far you have not given any reason why that would not work for you.

Answer 2

[randerss simil]

%% pwds - different working directory - D:\matlabfiles\ACTIVITY\Itr 3\Script
eval(['save(fullfile(' pwds 'Batch_' num2str(i) '_Results_' simtype '.mat t' ')' ')']);

Requires closing parenthesis ... try above

[randerss simil]

Closing parenthesis for fullfile and save functions

[randerss simil]

Is Batch_ a directory ? if it is then use filesep also.

%% pwds - different working directory - D:\matlabfiles\ACTIVITY\Itr 3\Script
eval(['save(fullfile(' pwds filesep 'Batch_' num2str(i) '_Results_' simtype '.mat t' ')' ')']);

[Gopinath Karuppannan]

Hi randerss,

Thanks for quick reply on this.

But still i am getting error while your code.

FYI: Is Batch_ a directory ? --> No it is not a directory. I want to save my workspace variables as Batch_1_Results_gopi.mat in my different working directory as a .mat file.

[randerss simil]

What error do you get ?

[randerss simil]

You shud follow image analyst answer. Read the tips section of the eval function in below link

https://www.mathworks.com/help/matlab/ref/eval.html

[Gopinath Karuppannan]

I am getting error as

% Error: Invalid use of operator

Okay thanks, I will use as per image analyst answer.