Introduction to MATLAB

M. Anand M.Tech.Assistant Professor (Sr. G)Dept. of Information TechnologySRM University

Introduction• MATLAB - MATRIX LABORATORY• Developed by MathWorks Inc. • Software package• Provides IDE for programming• Provides predefined functions for

technical computations and visualization

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Introduction (cont)• Uses:

– To perform scientific computations– Visualization– Analyze of various scientific problems

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Introduction (cont)• Provides a collection of functions

(tools) for specific applications – Image processing– Neural Networks– Control System– Digital Signal Processing, etc.• A collection of programs are called

“Toolboxes”

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Introduction (cont)• The basic building block in MATLAB

is matrix• Basic data type(matrix) is defined as

an array• Vectors, scalars etc. are

automatically handled as matrices

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Introduction (cont)• Scalars are treated as a matrix of

single row and single column• A single row matrix is treated as row

vector • A single-column matrix are treated

as column vector

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Introduction (cont)• No need to declare the dimensions

of a matrix• No need to declare any variables

and their types• MATLAB automatically sets the type

of the variable according to the type of value assigned to that variable

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Introduction (cont)• MATLAB is platform independent• Supported by Windows and

UNIX/LINUX operating systems• MATLAB programs are portable

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Starting a MATLAB Session• Double click on the shortcut on the

desktopOr

• Double click on any MATLAB generated file (.m, .mat, .mdl, .fig)

Or• Click on the Start Button Select

Programs Select MATLAB Click on R2008b

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Ending a MATLAB Session• Select File Exit

Or• Type quit or exit in the command

window

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MATLAB Environment• Components of the MATLAB

environment– Command Window– Command History– Workspace– Current Directory– Figure Window– Edit Window

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Command Window• Command window is the main

window• Displays the command prompt ‘>>’• Commands are executed

instantaneously>> 30*3+7ans =

97>>

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Command Window• Result stored in a default variable,

‘ans’• Result can be assigned to a variable

>> x = 30 * 3 + 7x =

97>>

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Command Window• If the output of a statement is not

needed to be displayed, add ‘;’ at the end of the statement

>> x = 30 * 3 + 7 ;>>

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Command Window• Find the value of z for the expression

z = x * y, if x = 5 and y = 3>> x=5;>> y=3;>> z=x*y;>> zz =

15>>

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Command History Window• Lists the commands entered in the

Command Window• The commands may be executed by

selecting and double clicking it• A program file may be created by

selecting a set of commands and right clicking it and selecting ‘Create M-file’ option from the pop-up menu

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Command History Window• To delete commands right click the

command and select ‘Delete Selection’

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Workspace• Lists collection of all the variables in

the current MATLAB session• Shows their data type and size• Commands to get the workspace

information

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Workspace (Cont)• who

– Lists all the variables in the workspace• whos

– Lists all the variables in the workspace with their size, number of bytes, and class/type of variable

• whos global– Lists the variables in the global

workspace

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Workspace (Cont)• whos –file filename

– Lists the variables in the specified .mat file

• whos var1 var2 . . .– Lists the details of the particular

variables

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Current Directory• Lists all the files and folders present

in the current directory• To run any file, it must either be in

the Current Directory or on the search path

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Edit Window• Used to create a new program file• Extension (.m)• To create a new M-File

File New M-File• To open an existing M-File

File Open• To save the content

File Save

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Edit Window• The saved M-file is executed by

typing its name without the extension in the Command window

• Edit Window can also be used to debug programs

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Figure Window• Used to display MATLAB graphics• Results of all the graphic commands

are displayed in the Figure Window• Any number of Figure windows can

be opened depending upon the system memory

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Figure Window (Cont)• Example:

>> x = 0 : 0.05 : 20;>> y = sin(x);>> plot (x, y);

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Figure Window (Cont)

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Help Feature• To get information about any function

or command• Three methods:

1. Help Browser2. help command3. lookfor command

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Help Browser• Select the Help icon from the toolbar

Or• Choose Help menu

Or• Type doc or helpdesk or helpwin in

the command window

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help Command• To obtain help for any particular

command• help command searches for an exact

function name match>> help sin

• Help command is useful when the name of the function is known

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help Command>> help

•Displays a list of all help topics and different toolboxes installed in the system

>> help help•Displays help about the help

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help Command• To list all the commands available in

the toolbox, use help followed by the name of the toolbox

>> help control systems

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lookfor Command• To obtain help on a particular topic • Searches the string in the first

command line of the help text in all the M-files found on the MATLAB path

• Slower than the help command• Provides more detailed useful

information

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lookfor Command• Useful when one is not sure about

which function perform a particular task

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Type of Files• Three types of files in the MATLAB:

1. M-files2. MAT-files3. MEX-files

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M-Files• Standard ASCII text files, with a (.m)

extension• Program written in the Edit window is

saved as M-files• Types of M-files

– Script files– Function files

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Script Files• An M-file with a set of valid MATLAB

commands is called a script file• To run a script file, the filename

without the (.m) is entered in the command window

• The script files work on global variables, that is, the variables currently present in the workspace

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Function Files• An M-file which begins with a

function definition line is called a function file

• If a file does not begin with function definition line, it becomes a script file

• Function files can be called from the script files or another function file

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MAT-files• MAT-files are binary data-files• .mat extension• Cannot be read by the user directly• Created when the data is saved

using save command• Save command saves data from the

current MATLAB workspace into a disk file

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MAT-files• Syntaxsave <filename> <var1 var2 var3 . . .>

• Load command loads data from the file into the current MATLAB workspace

• Syntaxload <filename>

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MEX-files• MEX-file is MATLAB callable

FORTRAN and C program, with a (.mex) extension

• Allows the user to integrate the code written in FORTRAN or C language into the programs developed using MATLAB

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Search Path• The ‘search path’ guides MATLAB to

locate the appropriate program for executing the command

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Search Path• Whenever a ‘word’ is entered at the

command prompt, the MATLAB follows the following steps in order to interpret it correctly:– First, it is assumed that the word is a

variable, if found in workspace, MATLAB displays its contents in the command window

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Search Path– If it is not a variable name, it is

assumed as a built-in function or command, if found, it is executed by the MATLAB

– If it is not a built-in function or command, then MATLAB checks the Current Directory if there is an M-file by that name. If found, it is executed

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Search Path– If it is not present in Current Directory

then MATLAB searches for the M-file in all folders and directories in the sequence given on the MATLAB search path. If found, it is executed

– If the word does not match anywhere, it responds by indicating that such a function or variable is not defined.

• Note: Use different names for variables, functions and files

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Search Path• To execute a script file, it must be

included in Current Directory or search path of MATLAB

• To add the folder in the search path select File ’Set Path’

• To add the selected directory and all of its subdirectoriesclick Add with subfolders option

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Search PathThe path-related commands are•addpath

– Adds directory to MATLAB search path•path

– Displays MATLAB search path

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MATLAB Commands1. General Commands•clock

– Provides clock time and date as a vector

•date– Provides date as a string

•ver– Gives the version of MATLAB installed

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MATLAB Commands (Cont)2. Directory Commands•dir

– Lists the files/folders in the Current Directory (MSDOS)

•ls– Lists the files/folders in the Current

Directory (Unix)•pwd

– Provides present working directory (Unix)

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MATLAB Commands (Cont)• path

– Displays MATLAB search path• editpath

– Modifies MATLAB search path• mkdir

– Makes a directory/folder (MSDOS)– Eg.: mkdir folder1

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MATLAB Commands (Cont)• cd

– Change present working directory (MSDOS)

• copyfile– Copies a file

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MATLAB Commands (Cont)3. Workspace Commands•who

– Lists the variables currently in the workspace/memory

•whos– Same as who command but gives type

and size

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MATLAB Commands (Cont)• what

– Lists .m, .mat, .mex files on the disk• clear all

– Clears the variables in the workspace• clear xyz

– Clears the variables specified in the command

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MATLAB Commands (Cont)• mlock fun

– Locks function fun so that it cannot be deleted

• clc– Clears screen

• clf– Clears Figure Window

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MATLAB Commands (Cont)4. Termination Commands•Ctrl+c

– Stops executing of function/command being run currently

•quit– Quits MATLAB

•exit– Same as quit command

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MATLAB Commands (Cont)5. help commands•help

– Lists the topics for which help is available

•help topic– Provides help for the topic specified in

the command

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MATLAB Commands (Cont)• lookfor string

– Lists the comment line of all .m files containing the string specified in the command

• helpwin– Opens the help window

• helpdesk– Opens the web browser for online help

• demo– Runs the demo program

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Thank You

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