matlab editor - tools/matlab/matlab_seminar2.pdf · pdf fileadvanced programming...

2 - 1Advanced Programming Techniques in MATLAB

2002 The MathWorks, Inc.

>> edit % Opens new file OR brings editor into focus>> edit welcomefile % Opens file named welcomefile.m

MATLAB Editor

2 - 2Advanced Programming Techniques in MATLAB

2002 The MathWorks, Inc.

% Comments start with "%" character

pause % Suspend execution. Press any key to continue.

keyboard % Pause & return control to command line.% Type "return" to continue.

break % Terminate execution of current loop/file.

return % Return to invoking function/command line.

input % Prompt for user input.

% Comments start with "%" character

pause % Suspend execution. Press any key to continue.

keyboard % Pause & return control to command line.% Type "return" to continue.

break % Terminate execution of current loop/file.

return % Return to invoking function/command line.

input % Prompt for user input.

Script M-Files Are standard ASCII text files Contain a series of MATLAB expressions(Typed as you would at the command line)

Commands are parsed and executed in order

2 - 3Advanced Programming Techniques in MATLAB

2002 The MathWorks, Inc.

Example: Script M-Filesdisp('I''m thinking of a number from 1 to 10.');secretNum = fix(10*rand + 1); % Will be integer.keyboardguessed = false;while ~guessed

thisGuess = input('Guess, or type -1 to give up: ');if thisGuess == secretNum

guessed = true;return

elseif thisGuess == -1break

elsedisp('Wrong! Try again.');

endend

>> numguess

2 - 4Advanced Programming Techniques in MATLAB

2002 The MathWorks, Inc.

Functions Core MATLAB (built-in) functions

sin, abs, exp, etc. MATLAB supplied M-file functions

mean, std, etc. User-created M-file functions

Wherever your imagination takes you...

Differences between script and function M-files Structural syntax Function workspaces, inputs, and outputs

2 - 5Advanced Programming Techniques in MATLAB

2002 The MathWorks, Inc.

function y = mymean(x)

%MYMEAN Average or mean value.

% For vectors, MYMEAN(x) returns the mean value.

% For matrices, MYMEAN(x) is a row vector

% containing the mean value of each column.

[m,n] = size(x);

if m == 1

m = n;

end

y = sum(x)/m;

function y = mymean(x)

%MYMEAN Average or mean value.

% For vectors, MYMEAN(x) returns the mean value.

% For matrices, MYMEAN(x) is a row vector

% containing the mean value of each column.

[m,n] = size(x);

if m == 1

m = n;

end

y = sum(x)/m;

Structure of a Function M-fileKeyword: function Function Name (same as file name .m)

Output Argument(s) Input Argument(s)

Online Help

MATLABCode

>> output_value = mymean(input_val)

Command Line Syntax

2 - 6Advanced Programming Techniques in MATLAB

2002 The MathWorks, Inc.

Subfunctions Using subfunctions allows more than one

function to be within the same M-file (modularize code).

M-files containing subfunctions must have the name of the first (primary) function.

Subfunctions can only be called from within the same M-file.

Each subfunction has its own workspace.

The file stats.m is an example of a function M-file with a subfunction.

>> edit stats

2 - 7Advanced Programming Techniques in MATLAB

2002 The MathWorks, Inc.

Private Functions Reside in a subdirectory named private Only accessible to functions in parent directory

Only accessible to functions inparent directory.private

directory

>> mytest2

2 - 8Advanced Programming Techniques in MATLAB

2002 The MathWorks, Inc.

MATLAB Calling Priority

HighVariableBuilt-in functionSubfunctionPrivate functionFiles

Mex-fileP-fileM-file

Low

>> cos='This string.';

>> cos(8)

ans =

r

>> clear cos

>> cos(8)

ans =

-0.1455

>> cos='This string.';

>> cos(8)

ans =

r

>> clear cos

>> cos(8)

ans =

-0.1455

2 - 9Advanced Programming Techniques in MATLAB

2002 The MathWorks, Inc.

Flow Control Constructs Logic control:

if / elseif / else switch / case / otherwise

Iterative loops: for while

2 - 10Advanced Programming Techniques in MATLAB

2002 The MathWorks, Inc.

if I == J

A(I,J) = 2;

elseif abs(I-J) == 1

A(I,J) = -1;

else

A(I,J) = 0;

end

if I == J

A(I,J) = 2;

elseif abs(I-J) == 1

A(I,J) = -1;

else

A(I,J) = 0;

end

Logical Control ProgrammingConstructs

switch algorithm

case 'ode23'

str = '2nd/3rd order';

case {'ode15s', 'ode23s'}

str = 'stiff system';

otherwise

str = 'other algorithm';

end

switch algorithm

case 'ode23'

str = '2nd/3rd order';

case {'ode15s', 'ode23s'}

str = 'stiff system';

otherwise

str = 'other algorithm';

end

>> if_examp>> switch_examp

Work on conditional statements Short-circuited in MATLAB - once a condition is true, or case

matched, the sequence terminates. switch-case statements are more efficient than if-elseif

statements when working with strings.

2 - 11Advanced Programming Techniques in MATLAB

2002 The MathWorks, Inc.

Iterative Loops

I = 1; N = 10;

while I while_examp

Similar to other programming languages for -- Repeats loop a set number of times (based on index) while -- Repeats loop until logical condition returns FALSE Can be nestedN = 10;

for I = 1:N

for J = 1:N

A(I,J) = 1/(I+J-1);

end

end

N = 10;

for I = 1:N

for J = 1:N

A(I,J) = 1/(I+J-1);

end

end

2 - 12Advanced Programming Techniques in MATLAB

2002 The MathWorks, Inc.Options from the Breakpoints menu.

MATLAB Debugger

2 - 13Advanced Programming Techniques in MATLAB

2002 The MathWorks, Inc.

Example: Visual Debugging Set up your debugger to stop if an error occurs

Then run: >> status = bank_info(100,0)

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2002 The MathWorks, Inc.

Example: Visual Debugging (continued)

2 - 15Advanced Programming Techniques in MATLAB

2002 The MathWorks, Inc.

The MathWorks Inc.Natick, MA USA

GUIDEGraphical User Interface Design Environment

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2002 The MathWorks, Inc.

Section Outline Hands-on GUIDE Example Writing Callbacks Switchyard Programming

2 - 17Advanced Programming Techniques in MATLAB

2002 The MathWorks, Inc.

GUIDE Example (Final Product)

Static Text Box

Checkbox

Pushbuttons

Axes

Slider

UI Menu

Line Plot

2 - 18Advanced Programming Techniques in MATLAB

2002 The MathWorks, Inc.

Open GUIDE >> guide Collect UI Controls

2 - 19Advanced Programming Techniques in MATLAB

2002 The MathWorks, Inc.

GUIDE Tools

Push Button

Axes

Checkbox

Static Text Box

Slider Alignment Tool

Menu Editor

Property InspectorObject Browser

Activate Figure

GUIDE Toolbar

Component Palette

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2002 The MathWorks, Inc.

Using the Property Inspector

>> gui_example

2 - 21Advanced Programming Techniques in MATLAB

2002 The MathWorks, Inc.

Writing CallbacksWhat is a callback? A sequence of commands that are executed when a graphics

object is activated. Stored as a text string and is a property of a graphics object.

(e.g. CreateFcn, ButtonDownFcn, Callback, DeleteFcn)

Components of a callback:1. get handles of the objects initiating action

(objects providing event / information / values)2. get handles of the objects being affected

(objects whose properties are to be changed) 3. get necessary information / values4. set relevant object properties to effect action

2 - 22Advanced Programming Techniques in MATLAB

2002 The MathWorks, Inc.

Callbacks (Example)

callback = ['pt = get(gca,''CurrentPoint'');'...

'xbox = findobj(''Tag'',''xbox'');' ...

'ybox = findobj(''Tag'',''ybox'');' ...

'set(xbox,''String'',num2str(pt(1,1)));'

callback = ['pt = get(gca,''CurrentPoint'');'...

'xbox = findobj(''Tag'',''xbox'');' ...

'ybox = findobj(''Tag'',''ybox'');' ...

'set(xbox,''String'',num2str(pt(1,1)));'

>> gui_example2

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2002 The MathWorks, Inc.

Using Callback Editor (Continued)

2 - 24Advanced Programming Techniques in MATLAB

2002 The MathWorks, Inc.

Using the Alignment Tool

1 Open Alignment Tool2 Select objects3 Select Align. Option(s)4 Apply/Revert Changes

2

4

3

4

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2002 The MathWorks, Inc.

Using Menu Editor

1 Open Menu Editor2 Add New Menu OR

New Menu Item3 Enter Label, Tag and

Callback Commands4 Apply Changes

Main MenuLabel = 'Load Data File'

Main MenuLabel = 'Load Data File'

Menu ItemLabel = 'MAT-File'

Callback:temp = cd;cd c:\class\matlab\examples;[filename, pathname] = uigetfile('*.mat'); load([pathname