Introduction to MATLAB

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# Introduction to MATLAB - PowerPoint PPT Presentation

Introduction to MATLAB Lecture 3: Data Visualization & User Interfaces Damon Tomlin February 22, 2008 A quick word about SPM . . . This can be a little intimidating . . . “Any sufficiently advanced technology is indistinguishable from magic.” -- Arthur C. Clarke, possibly describing SPM

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### Introduction to MATLAB

Lecture 3: Data Visualization & User Interfaces

Damon Tomlin

February 22, 2008

A quick word about SPM . . .

This can be a little intimidating . . .

-- Arthur C. Clarke, possibly describing SPM

• SPM is three things:
• Some functions that work on numbers (your data)
• Some functions that display the crunched numbers
• A bunch of buttons that run the functions when you press them
Overview of MATLAB Graphics
• Figures
• Axes
• UI Objects
• Handles
• If you can see it, it has a handle.
• Some things you can’t see have handles, too.
• Use handles to manipulate properties.
Handles & Properties
• Figures, axes, and graphics have handles, just like files
• These objects have properties
• These properties can be altered
How many ways can we look at data?
• 2D line plots
• Pseudocolor Images
• Histograms
• 3D shapes
2D Plots
• plot(x,y);
• plot([x1 x2 x3],[y1 y2 y3]);
• plot(x1,y1,’r.’,x2,y2,’b-’);
Images
• imagesc
• Pseudocolor
• Colormaps
• image
• M x N x 3 matrix
Histograms
• hist
• designate bins
• bar
• generic bar graph
3D Visualization
• Surface plots
• Color
• Transparency
• Mesh plots
• 3D shapes
• xlabel, ylabel, zlabel
• title
• legend
Other handy functions
• subplot(rows,columns,number)
• Axis([xmin xmax ymin max])
• set(handle,’PropertyName’,value, . . .);
• get(handle,’PropertyName’)
What’s a Graphical User Interface? (GUI)
• Figure windows
• Buttons, menus, sliders, etc.
• Appearance changes depending on inputs & outputs
• Eliminates command line typing
Demystifying GUI’s
• Interface objects have properties
• Style – type of object
• String – text associated with object
• Callback – what the object does
• Value – current value of object
• What these properties mean depends on the type (Style) of object created
UI Styles: Buttons
• Buttons cause commands to be executed
• Style – pushbutton
• String – text on the button
• Callback – string containing command(s) executed by button
• Value – not important
The Eval Function
• Executes a string as though it were a command typed into a command window or function
• Example 1: eval(‘disp(a);’);
• Example 2: eval([‘save ‘ FileName ‘ a b;’]);
Callbacks and Eval
• Callbacks are assigned within functions
• Callbacks are executed outside functions
• (usually)
• Therefore, any variables a callback needs have to be stored somehow.
UI Styles: Radio Buttons
• Style – radiobutton
• String – text on the button
• Value – whether button is pushed in or out
• Callback – exclusivity code & additional functions
• Used in sets for mutually exclusive, boolean options
UI Styles: Check Boxes
• Style – checkbox
• String – text on the box
• Value – whether button is checked
• Callback – often nothing, unless switching the option’s value executes a function
• Used for boolean options
UI Styles: Edit Windows
• Style – edit
• String – text in the box
• Value – not used
• Callback – function executed when Enter key is pressed
• Used for typed inputs of names & values
UI Styles: Slider Bars
• Style – slider
• String – not used
• Value – position of slider – between Max and Min
• Callback – function executed when slider is moved
• Used when a variable can take on a spectrum of values
UI Styles: Text Boxes
• Style – text
• String – text in the box
• Value – not used
• Callback – not used
• Used for displaying information, entitling portions of a GUI
UI Styles: Frames
• Style – Frame
• String – not used
• Value – not used
• Callback – not used
• Used for grouping other objects visually
UI Styles: List Boxes
• Style – listbox
• String – cell array of each possible choice
• Value – currently highlighted selection
• Callback – function executed when an item is selected
• Used for selecting options when their names and numbers may change
UI Styles: Pop Up Menus
• Style – popupmenu
• String – cell array of each possible choice
• Value – currently selected option
• Callback – function executed when an item is selected
• Used for selecting options in a more compact manner
Useful Functions
• set – change something’s properties
• get – find out what something’s properties
• guidata – attach data to/pull data from GUI
Summary
• MATLAB has lots of functions to help you look at your data
• You can connect functions to GUI’s so you don’t have to type as much
• As we’ll see, this is exactly what SPM does.