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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 . . . “Any sufficiently advanced technology is indistinguishable from magic.” -- Arthur C. Clarke, possibly describing SPM

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Introduction to MATLAB

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Introduction to matlab l.jpg

Introduction to MATLAB

Lecture 3: Data Visualization & User Interfaces

Damon Tomlin

February 22, 2008


A quick word about spm l.jpg

A quick word about SPM . . .

This can be a little intimidating . . .


Any sufficiently advanced technology is indistinguishable from magic l.jpg

“Any sufficiently advanced technology is indistinguishable from magic.”

-- 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 l.jpg

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 l.jpg

Handles & Properties

  • Figures, axes, and graphics have handles, just like files

  • These objects have properties

  • These properties can be altered


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How many ways can we look at data?

  • 2D line plots

  • Pseudocolor Images

  • Histograms

  • 3D shapes


2d plots l.jpg

2D Plots

  • plot(x,y);

  • plot([x1 x2 x3],[y1 y2 y3]);

  • plot(x1,y1,’r.’,x2,y2,’b-’);


Images l.jpg

Images

  • imagesc

    • Pseudocolor

    • Colormaps

  • image

    • M x N x 3 matrix


Histograms l.jpg

Histograms

  • hist

    • designate bins

  • bar

    • generic bar graph


3d visualization l.jpg

3D Visualization

  • Surface plots

    • Color

    • Transparency

  • Mesh plots

  • 3D shapes


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Making Visualizations More Informative

  • xlabel, ylabel, zlabel

  • title

  • legend


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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 l.jpg

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 l.jpg

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 l.jpg

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 l.jpg

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;’]);


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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 l.jpg

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 l.jpg

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


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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 l.jpg

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 l.jpg

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 l.jpg

UI Styles: Frames

  • Style – Frame

  • String – not used

  • Value – not used

  • Callback – not used

  • Used for grouping other objects visually


Ui styles list boxes l.jpg

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 l.jpg

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


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Useful Functions

  • set – change something’s properties

  • get – find out what something’s properties

  • guidata – attach data to/pull data from GUI


Summary l.jpg

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.


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