Lecture 1: Introduction

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Lecture 1 Introduction

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

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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.

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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.

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MATLAB desktop
Command Window Command History Window Workspace
Window Current Directory Window Start Button
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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

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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.

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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.

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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

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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

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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

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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!

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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

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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).

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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.

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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.

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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.

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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
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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.

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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!