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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
M. Anand 2
Introduction (cont)• Uses:
– To perform scientific computations– Visualization– Analyze of various scientific problems
M. Anand 3
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”
M. Anand 4
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
M. Anand 5
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
M. Anand 6
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
M. Anand 7
Introduction (cont)• MATLAB is platform independent• Supported by Windows and
UNIX/LINUX operating systems• MATLAB programs are portable
M. Anand 8
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
M. Anand 9
MATLAB Environment• Components of the MATLAB
environment– Command Window– Command History– Workspace– Current Directory– Figure Window– Edit Window
M. Anand 11
Command Window• Command window is the main
window• Displays the command prompt ‘>>’• Commands are executed
instantaneously>> 30*3+7ans =
97>>
M. Anand 13
Command Window• Result stored in a default variable,
‘ans’• Result can be assigned to a variable
>> x = 30 * 3 + 7x =
97>>
M. Anand 14
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 ;>>
M. Anand 15
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>>
M. Anand 16
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
M. Anand 17
Command History Window• To delete commands right click the
command and select ‘Delete Selection’
M. Anand 18
Workspace• Lists collection of all the variables in
the current MATLAB session• Shows their data type and size• Commands to get the workspace
information
M. Anand 19
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
M. Anand 20
Workspace (Cont)• whos –file filename
– Lists the variables in the specified .mat file
• whos var1 var2 . . .– Lists the details of the particular
variables
M. Anand 21
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
M. Anand 22
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
M. Anand 23
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
M. Anand 24
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
M. Anand 25
Help Feature• To get information about any function
or command• Three methods:
1. Help Browser2. help command3. lookfor command
M. Anand 28
Help Browser• Select the Help icon from the toolbar
Or• Choose Help menu
Or• Type doc or helpdesk or helpwin in
the command window
M. Anand 29
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
M. Anand 30
help Command>> help
•Displays a list of all help topics and different toolboxes installed in the system
>> help help•Displays help about the help
M. Anand 31
help Command• To list all the commands available in
the toolbox, use help followed by the name of the toolbox
>> help control systems
M. Anand 32
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
M. Anand 33
lookfor Command• Useful when one is not sure about
which function perform a particular task
M. Anand 34
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
M. Anand 36
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
M. Anand 37
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
M. Anand 38
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
M. Anand 39
MAT-files• Syntaxsave <filename> <var1 var2 var3 . . .>
• Load command loads data from the file into the current MATLAB workspace
• Syntaxload <filename>
M. Anand 40
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
M. Anand 41
Search Path• The ‘search path’ guides MATLAB to
locate the appropriate program for executing the command
M. Anand 42
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
M. Anand 43
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
M. Anand 44
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
M. Anand 45
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
M. Anand 46
Search PathThe path-related commands are•addpath
– Adds directory to MATLAB search path•path
– Displays MATLAB search path
M. Anand 47
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
M. Anand 48
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)
M. Anand 49
MATLAB Commands (Cont)• path
– Displays MATLAB search path• editpath
– Modifies MATLAB search path• mkdir
– Makes a directory/folder (MSDOS)– Eg.: mkdir folder1
M. Anand 50
MATLAB Commands (Cont)• cd
– Change present working directory (MSDOS)
• copyfile– Copies a file
M. Anand 51
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
M. Anand 52
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
M. Anand 53
MATLAB Commands (Cont)• mlock fun
– Locks function fun so that it cannot be deleted
• clc– Clears screen
• clf– Clears Figure Window
M. Anand 54
MATLAB Commands (Cont)4. Termination Commands•Ctrl+c
– Stops executing of function/command being run currently
•quit– Quits MATLAB
•exit– Same as quit command
M. Anand 55
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
M. Anand 56
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
M. Anand 57