MATLAB: Undefined function error is very slow to occur

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Whenever I type or have a script/M-file with an undefined function or variable (usually through a typo), MATLAB takes about 40 seconds to return the 'Undefined function or variable' message. For example:
>> fg
Undefined function or variable 'fg'.
If I turn off internet access, the delay in producing the message does not occur.

Best Answer

This is most likely due to having network locations on your MATLAB path. While connected to the internet, MATLAB searches through all of these paths before concluding that no such variable/function exists. When not connected to the internet, MATLAB is forced to ignore any network locations. To check this, you can restore the default MATLAB path. Please note that if you have custom paths that you would like to keep on your MATLAB path, you may want to back them up first. See this MATLAB Answers post for more details:
https://www.mathworks.com/matlabcentral/answers/166871-how-will-running-the-restoredefaultpath-and-savepath-commands-affect-my-custom-paths-and-how-do-i-ba
To restore the default MATLAB path, execute the following in the MATLAB Command Window and then restart MATLAB:
>> restoredefaultpath
>> rehash toolboxcache
>> savepath
If this does not correct the issue, then you may have some network locations in your history. You can clear your history by executing the following and then restarting MATLAB:
>> s = settings;
>> s.matlab.desktop.currentfolder.History.PersonalValue = {''}
You can also change the maximum size of your history, so that MATLAB will not store as many locations. To do this, execute the following code and restart MATLAB:
>> s = settings:
>> s.matlab.desktop.currentfolder.HistorySize.PersonalValue = 20; % you can adjust this value
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