4. MATLAB Dr. Kashif Mahmood Rajpoot

SEECS, NUST Islamabad kashif.rajpoot@seecs.edu.pk

NUST Science Society (NSS) Workshop

Workshop Contents: Session 4

• GUI: Controls, static element, axes, menus, callbacks, hObject, eventdata, handles, figures, GUIDE, Property Inspector, guidata, dialog boxes

• Simulink

• Conclusion

GUI

• GUI – a pictorial interface to a program

– Make programs easier to use with intuitive controls (buttons, text, lists, menus, etc)

– Easy interaction with mouse

GUI – Principal elements • GUI Components

– Controls (push buttons, edit boxes, lists, etc.)

– Static elements (frames, text strings)

– Menus

– Axes

• Figures – GUI components are arranged within a Figure which is a window on

computer screen

• Callbacks – A way to respond to any user interaction (mouse or keyboard input) or

event

– Code executed in response to an event is known as callback

– There must be a callback to implement the function of each GUI component

Creating and displaying a GUI

• MATLAB GUIs are created using a tool called guide, the GUI Development Environment

– guide allows the programmer to layout GUI components

• Once the GUI components are in place, the programmer can edit their properties (name, size, color, text, etc.)

• Upon saving, guide creates a working MATLAB program that programmer can modify to implement the behavior of GUI

Creating and displaying a GUI 1. Decide the elements required for GUI and the

function of each element. Make a rough layout. 2. Use MATLAB tool guide to lay out the

components on a Figure. 3. Use the Property Inspector to give each

component a unique name (‘tag’) and set other characteristics (color, text, etc.)

4. Save. This creates 2 files: .fig (containing the actual GUI) and .m (containing the code to load the figure and callbacks)

5. Write code for implementing the action behavior associated with each callback function.

MyFirstGUI

• Create a GUI that inputs two numbers and shows the result of their addition

Structure of callback subfunction function MyFirstButton_Callback(hObject,

eventdata, handles)

hObject – handle to parent figure

eventdata – reserved variable, not for our use

handles – a structure containing the handles of all GUI components on the figure and any user-defined application data

• Note that each callback function has access to handles structures and can modify any GUI component

Dialog boxes

• Dialog box – a special type of figure used to display information or to get input from user

– Modal – does not allow other windows to be accessed until it is dismissed. Typically used for error messages which need urgent attention.

– Non-modal - does not block access to other windows

Menus

• Menu – allows a user to select actions from a list of choices without additional components appearing on the GUI

• MATLAB menus are created using Menu Editor

• Suppressing the default menu

– Set ‘MenuBar’ property of Figure to ‘none’

MATLAB GUI

• GUI components are created using the guide tool

• The GUI components can be set by setting the characteristics in the Property Inspector

• The callback functions are written in the m-file to implement the action behavior of GUI components

Practice GUI

Simulink

• Simulating a dynamic system

• Simulink is a MATLAB add-on that facilitates

– Simulation by graphical building-blocks, without knowing any bit of MATLAB programming

Simulink

• Sources – Originator of data (e.g. file, workspace, etc)

• Sinks – Terminator of data (e.g. file, display screen)

• Image processing example – Thresholding

– Edge detection

– Rotation

Conclusion

• MATLAB is a wonderful and easy-to-use environment

– Scientific computations

– Visualization (i.e. plotting)

– Prototyping

• MATLAB Central File Exchange