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Lecture 1: Introduction

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Title: Lecture 1: Introduction


1
Lecture 1 Introduction
  • Lecture series based on the text
  • Essential MATLAB
  • for Engineers and Scientists
  • By
  • Hahn Valentine
  • -------------------------------------------------

2
Objectives of course
  • Learn how to examine, explore and evaluate
    MATLAB.
  • Learn how to do technical computing with MATLAB.
  • Learn how to design programs to solve technical
    problems via structure plan (i.e., a design
    methodology).
  • Learn to formulate algorithms for the steps of
    the structure plan.
  • Learn how to translate the steps into computer
    programs to solve engineering and scientific
    problems.

3
Objective of this lecture
  • Provide an overview of some of the features of
    MATLAB as a way to begin your
  • Evaluation of this new technical computing tool.
  • Training in the art of computer programming.
  • Learning to use MATLAB as a notepad for
    mathematical computations that arise in
    engineering and science courses.

4
MATLAB desktop
Command Window Command History Window Workspace
Window Current Directory Window Start Button
5
Command Window
  • The Command Window on the right is the main panel
    where you interact with MATLAB.
  • You key (or type) and ltEntergt commands after the
    prompt gtgt MATLAB executes the commands and
    displays results (if requested).
  • Some commonly used tools and commands
  • ? (up arrow) returns last command input, can be
    repeated
  • clc clears the screen
  • whos shows list of variables
  • clear clears variables

6
Evaluation of MATLAB
  • HANDS-ON with MATLAB
  • Type
  • gtgt 23 ltEntergt
  • into the Command Window
  • gtgt clc ltEntergt
  • gtgt whos ltEntergt
  • Throughout the lecture, yellow text indicates
    what you should type into MATLAB.

7
Command History Window
  • The Command History Window logs all of the
    commands you enter in MATLAB.
  • It should have logged 23.
  • Use the Command History Window to reenter 23 in
    the command window (use copy-and- paste or double
    click on 23).
  • This is useful to retrieve past commands.
  • Use Shift key to select multiple lines.

8
Arithmetic with MATLAB
  • Let us explore by doing exercises
  • gtgt 32 ltEntergt
  • gtgt 32 ltEntergt
  • gtgt 3/2 ltEntergt
  • gtgt 3\2 ltEntergt
  • gtgt 32 ltEntergt
  • gtgt 2/0 ltEntergt
  • gtgt 0/2 ltEntergt
  • gtgt 3Inf ltEntergt

9
Algebraic-numeric computations
  • Let us explore by doing exercises
  • gtgt a 3 ltEntergt
  • gtgt b 2 ltEntergt
  • gtgt a b ltEntergt
  • gtgt a / b ltEntergt
  • gtgt a2 ltEntergt
  • gtgt c a b ltEntergt
  • gtgt d c(b1) ltEntergt
  • gtgt who

10
Hiding Output
  • Let us explore by doing exercises
  • gtgt clear clc ltEntergt
  • gtgt whos ltEntergt
  • gtgt a 3 ltEntergt
  • gtgt b 2 ltEntergt
  • gtgt c a b ltEntergt
  • gtgt d c(b1) ltEntergt
  • gtgt who ltEntergt
  • gtgt a, b, c, d are in workspaceltEntergt
  • gtgt a, b, c, d ltEntergt

11
Plot y versus x
  • Introduction to plotting displaying data
  • gtgt clear clc ltEntergt
  • gtgt x 00.11 ltEntergt
  • gtgt y x.2 ltEntergt
  • gtgt whos ltEntergt
  • gtgt plot(x,y,x,y,o) ltEntergt
  • gtgt disp(' '),disp('...... x ........ y
    .....'),disp(x y') ltEntergt
  • gtgt x ltEntergt
  • gtgt y ltEntergt
  • gtgt x and y are 1-by-11 arrays of numbers!

12
Write a Simple Program
  • Consider computing the volume of a cone
  • Volume (pi.r.2.h)./3
  • radius 6 inches
  • height 12 inches
  • In the command window key in
  • gtgt clear clc ltEntergt
  • gtgt r 6 ltEntergt
  • gtgt h 12 ltEntergt
  • gtgt v (pi.r.2.h)./3 ltEntergt
  • gtgt whos ltEntergt

13
Editor M-Files
  • An M-file in MATLAB is analogous to a txt-file in
    Microsoft Notepad.
  • An M-file is created in MATLAB text editor.
  • M-files
  • You can save your programs (i.e., list of
    executable commands) as M-files.
  • You can reopen and modify your program.
  • They are useful for debugging (correcting
    errors) as you develop your programs (your
    technical computing tools).

14
Comments in programs
  • Every time you write a program to be saved, it is
    helpful for you to comment (i.e., describe) it
    well.
  • To insert a comment on a line in the editor or in
    the Command Window, use the comment operator ,
    then type your comment.
  • MATLAB
  • will not run lines that begin with the comment
    operator (in the editor comments appear in
    green).
  • Comments
  • Comments allow you (and others) to more easily
    understand your program.
  • When your lines of code are easy to understand,
    your code will be easier to use later.

15
Art of well-written code
  • A well-written program is like literature it
    contains comments explaining
  • what your program requires as input.
  • what the variables in the program represent.
  • what your program computes and displays.
  • It is useful for you to add a set of header
    comments that include the name of the program,
    your name (as the programmer), and the date the
    program was created or modified.

16
Saving code in an M-File
  • Open the editor by
  • Entering the command edit in the command window.
  • Or click the white-sheet-of-paper icon in the
    upper left hand corner directly below file.
  • Now enter the lines of code to find the volume of
    a cone
  • rr 4
  • h 12
  • v (pi.r.2.h)./3
  • REMARK If you save it, add header comments and
    comments explaining what the program does.
  • After you have typed in the code, save it as
    cone.m.

17
This is cone.m in the editor
Tool to compute the volume of a cone. A
simple sample for a first lecture. B.H.
Daniel........... January 2007 rr 4
radius of the cone h 12 height of the cone v
(pi.r.2.h)./3 Volume of the cone
18
Execute an M-file as a Command
  • Now execute (or run) the program by pushing F5,
    or by typing on the command line
  • gtgt cone ltEntergt
  • or by clicking the run button. (Note that the
    run button looks like a page with a down arrow to
    its left. It can be found below help on the
    toolbar of the edit window.)
  • If you entered the code as written on the
    previous slide you will get an error!
  • What went wrong?
  • Repair your program (Change rr 4 to r 4.),
    save it, and run it again.
  • Now change the height to 24, save and run your
    program again.

19
Summary
  • MATLAB can be used like a hand calculator to do
    arithmetic.
  • You can define (or assign) variables with numbers
    and expressions to do calculations as illustrated
    by the volume-of-cone example.
  • The advantage of saving programs as M-files is
    that you open it, make changes and/or execute it
    again without having to type it all over again.
  • This concludes our overview of MATLAB and a taste
    of things to come!
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