Matlab Training Session 13: Creating Gui’s

1. Matlab Training Session 13:Creating Gui’s Course Website: http://www.queensu.ca/neurosci/Matlab Training Sessions.htm

2. Course Outline Term 1 • Introduction to Matlab and its Interface • Fundamentals (Operators) • Fundamentals (Flow) • Importing Data • Functions and M-Files • Plotting (2D and 3D) Term 2 • Term 1 review • Plotting (2D and 3D) • Statistical Tools in Matlab • Nonlinear Curve Fitting • Statistical Tools in Matlab II • GUI’s

3. GUI • Graphical User Interface • A tool for interacting with the computer

4. How is this useful? • Visually interaction with data is often simpler and more intuitive • Faster manipulation of data • Interactive • Easy to Learn! • Fool Proof

5. Some Examples

6. Components of a GUI • Front End • point of interaction with user • Back End • where the action is, the code controlling the graphics and the different widgets

7. Components of a GUI • Front End • Select and place different objects (widgets) on the graphical layout. These will the what the user interacts with. • Underlying the GUI is the backend which controls how the GUI reacts on an event. • This is called event-driven programming

8. Components of a GUI • Back End • The code underlying the frontend graphics. • Matlab gives a basis and you fill in the details

9. In Matlab • Matlab provides interactive tool for creating the graphics and underlying code for GUIs • Function is called GUIDE • Provides some templates for simple GUIs that can be expanded as need be • Launch GUIDE in Matlab and select on of the pre-made templates (ie. not Blank)

10. GUI with Axis and Menu • This is the layout for a simple GUI that allows you to select one of 5 pre-made plots. • Not very useful but a good basis to start with • Press the Launch button and save • You will see the screen and you can interact with it

11. Backend of Axis and Menu • When you launch the GUI created the .fig file which is the graphics and the .m file which is the underlying code that control the widget. • Take a Look at the .m file • It looks like a mess, but it is not so bad! • Lets explore this code • First lets understand the basic m-file format template for an empty GUI

12. Functions and Callbacks in the M-File • Common Input Arguments • All functions in the M-file have the following input arguments corresponding to the handles structure: • hObject -- the handle to the figure or Callback object • handles -- structure with handles and user data • The handles structure is saved at the end of each function with the command: • guidata(hObject, handles);

13. Functions and Callbacks in the M-File • Sharing Data with the Handles Structure • When you run a GUI, the M-file creates a handles structure that contains all the data for GUI objects, such as controls, menus, and axes. • The handles structure is passed as an input to each callback (user interface). • You can use the handles structure to Share data between callbacks using the ‘guidata’ function

14. Functions and Callbacks in the M-File Sharing Data To store data that is contained in a variable X, set a field of the handles structure equal to X and then save the handles structure with the guidata function: handles.current_data = X; guidata(hObject,handles) You can retrieve the data in any other callback with the command: X = handles.current_data;

15. Functions and Callbacks in the M-File • You can add code to the following parts of the GUI M-file: • Opening function -- executes before the GUI becomes visible to the user. • Output function -- outputs data to the command line, if necessary. • Callbacks -- execute each time the user activates the corresponding component of the GUI.

16. Functions and Callbacks in the M-File • Opening Function • The opening function contains code that is executed just before the GUI is made visible to the user. • You can access all the components for the GUI in the opening function, because all objects in the GUI are created before the opening function is called. • You can add code to the opening function to perform tasks that need to be done before the user has access to the GUI • This includes: • creating data, plots or images, or making the GUI blocking with the uiwait command.

17. uiwait • The command uiwait makes the M-file halt execution • This is useful to force the program to pause execution until a user activates a some component in the GUI. • The uiresume command allows the M-file to resume execution once the user input is complete

18. Functions and Callbacks in the M-File • Opening Function • For a GUI whose file name is my_gui, the definition line for the opening function is: • function my_gui_OpeningFcn(hObject, eventdata, handles, varargin) • Besides the arguments hObject and handles, the opening function has the following input arguments: • eventdata -- reserved for a future version of MATLAB • varargin -- command line arguments to untitled

19. Functions and Callbacks in the M-File • Opening Function (varargin) • All command line arguments are passed to the opening function via varargin. • If you open the GUI with a property name/property value pair as arguments, the GUI opens with the property set to the specified value. • For example: • my_gui('Position', [71.8 44.9 74.8 19.7]) • opens the GUI at the specified position, since Position is a valid figure property

20. Functions and Callbacks in the M-File Output Function The output function returns output arguments to the command line. GUIDE generates the following output function: % --- Outputs from this function are returned to the command line. function varargout = my_gui_OutputFcn(hObject, eventdata, handles) % Get default command line output from handles structure varargout{1} = handles.output;

21. Functions and Callbacks in the M-File • Callbacks • When a user activates a component of the GUI, the GUI executes the corresponding callback. • The name of the callback is determined by the component's Tag property and the type of callback. • For example, a push button with the Tag print_button executes the callback: • function print_button_Callback(hObject, eventdata, handles)

22. Functions and Callbacks in the M-File • Output Function • By default the output is the handle to the GUI, which is assigned to handles.output in the opening function. • To make the GUI return a different output (eg. return the result of a user response, such as pressing a push button): • % Add the command uiwait to the opening function • % For each component of the GUI where you expect a user response, make the callback update the value of handles.output, and execute uiresume. • handles.output = ‘some response string'; • guidata(hObject, handles); • uiresume;

23. Property Inspector • Adjusts the details of the different widgets

24. Something Useful? • Now, lets try and build something that we may actually use. How about a simple program that combines loading, plotting and calculating some simple statistics on preformatted data • Create a GUI that will load ‘week8_testdata2.txt’, plot the data points as well as a linear regression Hint, All you need are simple push buttons and an axis for plotting

25. Programming GUI controls • Push Buttons • Work like independent functions • Each button function is passed all data from the GUI handles • % --- Executes on button press in Exit. • function Exit_Callback(hObject, eventdata, handles) • % hObject handle to Exit (see GCBO) • % eventdata reserved - to be defined in a future version of MATLAB • % handles structure with handles and user data (see GUIDATA) • close gcf • Detailed descriptions of all GUI callback controls can be found within the GUIDE help menu.

26. Layout the GUI