Matlab - Primer.pdf - Matlab - emdaka

MATLAB Primer

Third Edition

Kermit Sigmon

Department of Mathematics

University of Florida

Department of Mathematics University of Florida Gainesville, FL 32611

sigmon@math.ufl.edu

1989, 1992, 1993 by Kermit Sigmon

On the Third Edition

The Third Edition of the MATLAB Primer is based on version 4.0/4.1 of MATLAB.

While this edition reﬂects an extensive general revision of the Second Edition, most sig-

nicant is the new information to help one begin to use the major new features of version

4.0/4.1, the sparse matrix and enhanced graphics capabilities.

The plain T E X source and corresponding PostScript le of the latest printing of the

MATLAB Primer are always available via anonymous ftp from:

Address: math.ufl.edu Directory: pub/matlab Files: primer.tex, primer.ps

You are advised to download anew each term the latest printing of the Primer since minor

improvements and corrections may have been made in the interim. If ftp is unavailable

to you, the Primer can be obtained via listserv by sending an email message to list-

serv@math.ufl.edu containing the single line send matlab/primer.tex.

Also available at this ftp site are both English (primer35.tex, primer35.ps)and

Spanish (primer35sp.tex, primer35sp.ps) versions of the Second Edition of the Primer,

which was based on version 3.5 of MATLAB. The Spanish translation is by Celestino

Montes, University of Seville, Spain. A Spanish translation of the Third Edition is under

development.

Users of the Primer usually appreciate the convenience and durability of a bound copy

with a cover, copy center style.

(12-93)

1989, 1992, 1993 by Kermit Sigmon

The MATLAB Primer may be distributed as desired subject to the following con-

ditions:

1. It may not be altered in any way, except possibly adding an addendum giving

information about the local computer installation or MATLAB toolboxes.

2. It, or any part thereof, may not be used as part of a document distributed for

a commercial purpose.

In particular, it may be distributed via a local copy center or bookstore.

Department of Mathematics

University of Florida

Gainesville, FL 32611

sigmon@math.ufl.edu

Introduction

MATLAB is an interactive, matrix-based system for scientic and engineering numeric

computation and visualization. You can solve complex numerical problems in a fraction of

the time required with a programming language such as Fortran or C. The name MATLAB

is derived from MATrix LABoratory.

The purpose of this Primer is to help you begin to use MATLAB. It is not intended

to be a substitute for the User's Guide and Reference Guide for MATLAB. The Primer

can best be used hands-on. You are encouraged to work at the computer as you read the

Primer and freely experiment with examples. This Primer, along with the on-line help

facility, usually suce for students in a class requiring use of MATLAB.

You should liberally use the on-line help facility for more detailed information. When

using MATLAB, the command help functionname will give information about a specic

function. For example, the command help eig will give information about the eigenvalue

function eig. By itself, the command help will display a list of topics for which on-line

help is available; then help topic will list those specic functions under this topic for which

help is available. The list of functions in the last section of this Primer also gives most of

this information. You can preview some of the features of MATLAB by rst entering the

command demo and then selecting from the options oered.

The scope and power of MATLAB go far beyond these notes. Eventually you will

want to consult the MATLAB User's Guide and Reference Guide. Copies of the complete

documentation are often available for review at locations such as consulting desks, terminal

rooms, computing labs, and the reserve desk of the library. Consult your instructor or your

local computing center to learn where this documentation is located at your institution.

MATLAB is available for a number of environments: Sun/Apollo/VAXstation/HP

workstations, VAX, MicroVAX, Gould, PC and AT compatibles, 80386 and 80486 com-

puters, Apple Macintosh, and several parallel machines. There is a relatively inexpensive

Student Edition available from Prentice Hall publishers. The information in these notes

applies generally to all of these environments.

MATLAB is licensed by The MathWorks, Inc., 24 Prime Park Way, Natick, MA 01760,

(508)653-1415, Fax: (508)653-2997, Email: info@mathworks.com.

1989, 1992, 1993 by Kermit Sigmon

Contents

Page

1. Accessing MATLAB ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: 1

2. Entering matrices :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: 1

3. Matrix operations, array operations :::::::::::::::::::::::::::::::::::::::::::::: 2

4. Statements, expressions, variables; saving a session ::::::::::::::::::::::::::::::: 3

5. Matrix building functions :::::::::::::::::::::::::::::::::::::::::::::::::::::::: 4

6. For, while, if | and relations :::::::::::::::::::::::::::::::::::::::::::::::::::: 4

7. Scalar functions ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: 7

8. Vector functions ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: 7

9. Matrix functions ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: 7

10. Command line editing and recall ::::::::::::::::::::::::::::::::::::::::::::::::: 8

11. Submatrices and colon notation :::::::::::::::::::::::::::::::::::::::::::::::::: 8

12. M-les: script les, function les ::::::::::::::::::::::::::::::::::::::::::::::::: 9

13. Text strings, error messages, input :::::::::::::::::::::::::::::::::::::::::::::: 12

14. Managing M-les ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: 13

15. Comparing eciency of algorithms: ﬂops, tic, toc ::::::::::::::::::::::::::::::: 14

16. Output format ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: 14

17. Hard copy :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: 15

18. Graphics ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: 15

planar plots (15), hardcopy (17), 3-D line plots (18)

mesh and surface plots (18), Handle Graphics (20)

19. Sparse matrix computations :::::::::::::::::::::::::::::::::::::::::::::::::::: 20

20. Reference :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: 22

iii

1. Accessing MATLAB.

On most systems, after logging in one can enter MATLAB with the system command

matlab and exit MATLAB with the MATLAB command quit or exit. However, your

local installation may permit MATLAB to be accessed from a menu or by clicking an icon.

On systems permitting multiple processes, such as a Unix system or MS Windows,

you will nd it convenient, for reasons discussed in section 14, to keep both MATLAB

and your local editor active. If you are working on a platform which runs processes in

multiple windows, you will want to keep MATLAB active in one window and your local

editor active in another.

You should consult your instructor or your local computer center for details of the local

installation.

2. Entering matrices.

MATLAB works with essentially only one kind of object|a rectangular numerical

matrix with possibly complex entries; all variables represent matrices. In some situations,

1-by-1 matrices are interpreted as scalars and matrices with only one row or one column

are interpreted as vectors.

Matrices can be introduced into MATLAB in several dierent ways:

Entered by an explicit list of elements,

Generated by built-in statements and functions,

Created in a diskle with your local editor,

Loaded from external data les or applications (see the User's Guide).

For example, either of the statements

A=[123;456;789]

and

A=[

123

456

789]

creates the obvious 3-by-3 matrix and assigns it to a variable A . Try it. The elements

within a row of a matrix may be separated by commas as well as a blank. When listing a

number in exponential form (e.g. 2.34e-9), blank spaces must be avoided.

MATLAB allows complex numbers in all its operations and functions. Two convenient

ways to enter complex matrices are:

A = [1 2;3 4] + i*[5 6;7 8]

A = [1+5i 2+6i;3+7i 4+8i]

When listing complex numbers (e.g. 2+6i) in a matrix, blank spaces must be avoided.

Either i or j may be used as the imaginary unit. If, however, you use i and j as vari-

ables and overwrite their values, you may generate a new imaginary unit with, say,

ii = sqrt(-1).

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