Engineering Applications

1
Engineering Applications

• Dr. Darrin Leleux
• Lecture 2 MATLAB Introduction
• Chapter 1

2
Introduction

• Class MATLAB Experience
• What is MATLAB
• The MATLAB System
• MATLAB Documentation

3
Typical Class MATLAB Experience
4
What is MATLAB?

• MATLAB is an acronym for Matrix Laboratory
• High-Performance Language for Technical Computing
• Typical uses Include
• Mathematics and computation
• Algorithm development
• Modeling, simulation, and prototyping
• Data analysis, exploration, and visualization
• Scientific and engineering graphics
• Application development, including graphical user
  interface (GUI) building

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The MATLAB System

• Development Environment
• The MATLAB Mathematical Function Library
• The MATLAB Language
• Handle Graphics
• The MATLAB Application Program Interface (API)
• Toolboxes
• MATLAB Central
• http//www.mathworks.com/matlabcentral/

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MATLAB Development Environment

• A set of tools and facilities that help use
  MATLAB functions and files
• MATLAB desktop
• Command Window
• Command History
• Browsers for viewing Help
• The Workspace
• Files (M-files, etc.)
• Search Path

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MATLAB Desktop
View or Change Current Directory
Enter MATLAB functions
Expand to view Documentation, demos, tools
Use tabs to go to Workspace browser
View or use previously run functions
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MATLAB Structure
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Example 1.1
maximum number of elements allowed in a matrix on
this version of MATLAB. My version 2.1475e009
Windows
10
Command Window

• Enter variables and run functions and M-files in
  interactive mode
• HINT use up-arrow to retrieve previously
  typed commands quickly

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Command History

• Lines entered in the Command Window are logged in
  this display
• You can view, copy and execute previously used
  functions
• Right Click on selection
• Copy
• Evaluate Selection
• Create M-file

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Workspace Browser

• Consists of the set of variables built up during
  a MATLAB session
• These can be saved off as a .mat file and loaded
  into MATLAB with the load command
• Save off variables using save command

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Array Editor

• Double-click on a variable in the Workspace
  browser to see it in the Array editor

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Launch Pad

• Provides easy access to tools, demos, and
  documentation
• Can also get to these via the Start menu

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Help Browser

• Search and view documentation
• It is also a Web Browser that displays HTML
• Consists of 2 panes, the Help Navigator (used to
  find information), and the display pane (for
  viewing information)

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Current Directory Browser

• View or change current directory
• Search for, view, open, or make changes to
  MATLAB-related folders and files.

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Search Path

• To determine how to execute functions
• Any file to run must reside in the search path
• To change the search path, select Set Path from
  the File menu on the desktop

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Editor/Debugger

• Create and debug M-files
• Provides a GUI for basic editing, as well as for
  M-file debugging

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MATLAB Mathematical Function Library

• Vast collection of computational algorithms
• Elementary functions, such as
• Sum
• Sine
• Cosine
• Complex arithmetic
• Advanced functions, such as
• Matrix inverse
• Matrix Eigenvalues
• Bessel functions
• Fast Fourier transforms

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MATLAB Language

• High-level matrix/array language
• Control flow statements
• Functions
• Data structures
• Input/output
• Object-oriented programming features

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Handle Graphics

• High-level commands
• 2-D 3-D data visualization
• Image processing
• Animation
• Presentation graphics
• Low-level graphics customization
• GUI building in MATLAB applications

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The MATLAB Application Program Interface (API)

• Library that allows users to write C and Fortran
  programs that interact with MATLAB
• Dynamic linking
• Calling MATLAB as a computational engine
• Reading/writing MAT-files

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MATLAB General Commands

• helpbrowser - Bring up the help browser.
• doc - On-line help, displayed in the
  help browser.
• help - M-file help, displayed at the
  command line.
• helpwin - M-file help, displayed in the
  help browser.
• lookfor - Search all M-files for keyword.
• syntax - Help on MATLAB command syntax.
• support - Open MathWorks Technical Support
  Web
• demo - Run demonstrations.
• ver - MATLAB, SIMULINK, and toolbox
  info.
• version - MATLAB version information.
• whatsnew - Access Release Notes.

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Example 1.2
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Managing the Workspace

• who - List current variables.
• whos - List current variables, long form.
• workspace - Display Workspace Browser, a GUI for
  managing
• the workspace.
• clear - Clear variables and functions from
  memory.
• All or just some of the variables
• pack - Consolidate workspace memory.
• load - Load workspace variables from
  disk.
• save - Save workspace variables to disk.
• quit - Quit MATLAB session.
• clc - Clear command window

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Example 1.3
MATLAB Script Example 1.3   gtgt Use of Strings
and eval gtgtf1exp(x) Define a string
function f1 exp(x) gtgtx1 2 3 x
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Managing commands and functions

• what - List MATLAB-specific files in
  directory.
• dir - List all files in current directory
• type - List M-file.
• edit - Edit M-file.
• open - Open files by extension. Does
  different tasks
• depending on extension type.
• which - Locate functions and files by path
• inmem - List functions in memory.
• mex - Compile MEX-function.

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Whats In An M-File
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Differences between Script M-files and Functions
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Block Comments
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Example 1.4
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Controlling the command window

• echo - Echo commands in M-files.
• more - Control paged output in command
  window.
• diary - Save text of MATLAB session.
• format - Set output format.
• beep - Produce beep sound.

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Operating System Commands

• cd - Change current working directory.
• copyfile - Copy a file or directory.
• movefile - Move a file or directory.
• delete - Delete file.
• pwd - Show (print) current working
  directory.
• dir - List directory.
• fileattrib - Get or set attributes of files and
  directories.
• isdir - True if argument is a directory.
• mkdir - Make directory.
• rmdir - Remove directory.
• getenv - Get environment variable.
• ! - Execute operating system command
• dos - Execute DOS command and return
  result.

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Operating System Commands(continued)

• unix - Execute UNIX command and return
  result.
• system - Execute system command and return
  result.
• perl - Execute Perl command and return
  result.
• web - Open Web browser on site or files.
• computer - Computer type.
• isunix - True for the UNIX version of
  MATLAB.
• ispc - True for the PC (Windows) version
  of MATLAB.

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Example 1.5 from Text

• M-file (EX1_5.M) to evaluate the function
• y aexp(-1.2t) - 3.0exp(-2t)
• INPUT Coefficient a and time t
• OUTPUT y(t) displayed
• fprintf('Compute y aexp(-1.2t) - 3.0exp(-2t)
  \n')
• ainput('Coefficient a, a ')
• tinput('Variable t, t ')
• Display results
• fprintf('\n Function ygexp(-1.2g)-3.0exp(-2
  g) \n',a,t,t)
• yaexp(-1.2t) - 3.0exp(-2t)
• End M-file

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Output of Example 1.5
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Debugging M-files

• debug - List debugging commands.
• dbstop - Set breakpoint.
• dbclear - Remove breakpoint.
• dbcont - Continue execution.
• dbdown - Change local workspace
  context.
• dbstack - Display function call stack.
• dbstatus - List all breakpoints.
• dbstep - Execute one or more lines.
• dbtype - List M-file with line numbers.
• dbup - Change local workspace
  context.
• dbquit - Quit debug mode.
• dbmex - Debug MEX-files (UNIX only).

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Control Flow

• if - Conditionally execute statements.
• else - IF statement condition.
• elseif - IF statement condition.
• end - Terminate scope of FOR, WHILE,
  SWITCH, TRY
• and IF statements.
• for - Repeat statements a specific
  number of times.
• while - Repeat statements an indefinite
  number of times.
• break - Terminate execution of WHILE or
  FOR loop.
• continue - Pass control to the next iteration
  of FOR or WHILE
• loop.
• switch - Switch among several cases based
  on expression.
• case - SWITCH statement case.
• return - Return to invoking function.

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For loop syntax

• for variable expression
• statement
• ...
• statement
• end
• EXAMPLE
• a zeros(k,k) Preallocate matrix
• for m 1k
• for n 1k
• a(m,n) 1/(mn -1)
• end
• end

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If syntax

• if expression1
• statements1
• elseif expression2
• statements2
• else
• statements3
• end

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While loop syntax
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Switch syntax
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Special variables and constants

• ans - Most recent answer.
• eps - Floating point relative
  accuracy.
• realmax - Largest positive floating point
  number.
• realmin - Smallest positive floating point
  number.
• pi - 3.1415926535897....
• i, j - Imaginary unit.
• inf - Infinity.
• NaN - Not-a-Number.
• isnan - True for Not-a-Number.
• isinf - True for infinite elements.
• isfinite - True for finite elements.
• why - Succinct answer.