Understanding how to edit the Matlab Gui call backs.

Referring to:

http://www.mathworks.com/help/matlab/creating_guis/write-callbacks-using-the-programmatic-workflow.html

Summarizing:

1.Function handles provide a way for you to represent a function as a variable in MATLAB.
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Actually you dont have to understand a lot. Its kinda high level job. Just make it work.