MATLAB-Introduction to Applications

7/30/2019 MATLAB-Introduction to Applications

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MATLAB

Introduction to Applications

Prasanta Sarkar

National Institutes of Technical Teachers

Training and Research, Kolkata


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Introduction to MATLAB

MATLAB is a high performance language for

technical computing. It integrates

computation, visualization, and programming.Typical uses include :

Math and computation

Algorithm development


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Data acquisition Modeling, simulation, and

prototyping

Data analysis, exploration, and visualization

Scientific and engineering graphics

Application development, including

graphical user interface building


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The MathWorks

Product Family

MATLAB

computational language,

Math and Visualization

SIMULINKGraphical Modelling,

simulation of continuous

and discrete systems

STATEFLOWSimulation of event

driven systems to

complement Simulink


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The MATLAB System

The MATLAB system consists of five main parts:

1. Development Environment: Set of tools and

facilities that help to use MATLAB functions and

files. Many of these tools are graphical user

interfaces. It includes the MATLAB desktop and

Command Window, a command history, an editor

and debugger, and browsers for viewing help, the

workspace, files, and the search path


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The MATLAB System

2. Mathematical Function Library: Vast

collection of computational algorithms ranging

from elementary functions, like sum, sine,cosine, and complex arithmetic, to more

sophisticated functions like matrix inverse,

matrix eigenvalues, Bessel functions, and fast

Fourier transforms.


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The MATLAB System

3. The Language: This is a high-level

matrix/array language with control flow

statements, functions, data structures,input/output, and object-oriented programming

features.

4. Graphics: Facilities for displaying vectors and

matrices as graphs. Two-dimensional and three-

dimensional data visualization, image processing,

animation, and presentation as well as to build

complete graphical user interfaces.


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The MATLAB System

5. Application Program Interface (API): This is

a library that allows to write C and Fortran

programs that interact with MATLAB. It includesfacilities for calling routines from MATLAB

(dynamic linking), calling MATLAB as a

computational engine, and for reading and writing

MAT-files


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Starting a MATLAB Session

Start a MATLAB Session from Desktop of acomputer

Click Start Button

All Programs

MATLAB 7.0.1

OR, Click MATLAB

icon on Desktop


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MATLAB Environment

Major components of MATLAB environment:

Command Window

Command History

Workspace

Current Directory

Figure Window

Edit Window


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MATLAB Environment

Default Desktop of MATLAB

Workspace

WindowCommand

Window

Command

History

Window


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MATLAB Environment

Execute the following statements using plot command

to get the Figure Window

x=0: 0.05: 30;y=cos (x);

plot (x, y)

FigureWindow


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Types of files

M-files - script & function files

script file : An M-file (with .m extension) with a setof MATLAB commands is called a script file which

may include user defined or built-in functions.

function file : An M-file beginning with a function

definition line is a function file which is run by

entering its name.


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Types of files

MAT-filesThese are binary data-files saved as *.mat file fromworkspace data and loaded into workspace by load

commandMDL-files

These are saved as *.mdl file for graphical extensionof MATLAB using simulink blocks

MEX-filesThese are FOTRAN / C programs (*.mex) callable byMATLAB to integrate code with it.


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Evaluating expression

command window displays a command prompt >>

and a cursor

Enter expression50*2 - 30/2 + 5

at the cursor

Push enter key

The result isstored in default

variable ans


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Creating and Saving M-file

Execute expression x=5, y=x+6, z=x+2*y

Select expression

in History Window Right click on it

Click create M-file

Edit Window will

pop up Save the file (with

.m extension) in

the Directory

C:\MATLAB7\work

Edit Window


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Execute a command

Execute the command

who or whos

It display currently used

variables as

Your variables are:

A ans x y z

Note that semi-colon(;)

after expression

do not display result

>> 50*2-30/2+5; x=5; y=x+6; z=x+2*y;

>> A=[1 4;2 5;3 6]'

A =

1 2 3

4 5 6

>> who

Your variables are:

A ans x y z

>> whos

Name Size Bytes Class

A 2x3 48 double array

ans 1x1 8 double array

x 1x1 8 double array

y 1x1 8 double array

z 1x1 8 double array

Grand total is 10 elements using 80 bytes


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Some MATLAB Commands

General Commands

clock - provide clock and time as a vector

date - provide a date string

ver - provide version of MATLAB

Directory Commands

pwd - present working directory

cd - change present working directory

dir / ls - list files/folders of current directory

path - display MATLAB search path

editpath - modify MATLAB search pathWorkspace Commands

who / whos - variables currently in workspace

what - list types of files .m, .mat, .mex


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Some MATLAB Commands

Workspace Commands

clear all - clear the variables on workspace

mlock fun - locks function fun to avoid deletion

clc - clears screen

clf - clears figureTermination Commands

ctrl + c - stop execution being run

quit - quits MATLAB

exit - same as quit

Help Commands help - list the help topic

help topic - list help on topic stated

lookfor string - list comment lines with string from all .m files

help matfun - list matrix functions of numerical linear algebra


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Character Set

Characters classified as :

Alphabets (case sensitive): A - Z, a - z

Numerals: 0 to 9

Special Characters: [ ] ( ) { } = ' . ... , ; : % !

@

White space characters: tab, blank, new line


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Data Types

Data types are in the form of array. Minimun single

element to an n-dimensional array

The char data type: hello , is a character array.Charstring is 1-by-n array

Numeric data type: int8, uint8, int16,uint16 include

signed and unsigned integer arrays.


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Data Types

Cell array: Used for storing dissimilar kinds of

data

A=[ 1 2 7 8];B=[2 3 6; 6 3 8; 2 8 4];

C=zeros(2,3,3)

D_cell={A B C}; It is a cell array of three cells


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Data Types

Structure data type: data is stored in named

fields rather than cells

abc.name = Prasanta Sarkar

abc.age = 52

abc.sex = male


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Special Variables & Constants

ans Default variable name for results

pi Value of

eps Smallest incremental number

inf Infinity

NaN Not a number (0/0)

i and j i = j = square root of -1

realmin The smallest usable positive real number

realmax The largest usable positive real number nargin no. of input arguments in a function

nargout no. of output arguments in a function


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Display formats

MATLAB supports these formats for outputting numericalresults.

format long 16 digits

format short e 5 digits plus exponent

format long e 16 digits plus exponent

format hex hexadecimal

format bank two decimal digits

format + positive, negative or zero format rat rational number (513/6)

format short default display


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MATLAB AS A

CALCULATOR

Command window

>> 39*4.4+5

ans =

176.6000

Command window

The MATLAB command

The result.


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MATLAB AS A

CALCULATOR

39*4.4+5

ans =

176.6000

this is the MATLAB prompt.It indicates that MATLAB is

ready to accept yourcommand

The MATLAB command

This is the result.


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MATLAB Assignment

A=2.3

A =

2.3000

this is the MATLAB prompt.It indicates that MATLAB is

ready to accept your

command

The MATLAB command

This is the result of theMATLAB statement


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Scalar Assignment

A=[2.3]

A =2.3000

The square brackets [ ] are used to

define matrices. We can use them

for scalars too.

this creates a variable A and set

its value to 2.3

A=2.3

A =

2.3000


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Row vector

X =

2 3 7

X=[2,3 7 ] Space or comma are used toseparate elements in the same

row

The square braces areused to define a matrix


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MATLAB Statements

MATLAB Statement Remarks

C=5.66 C is a scalar

C=[5.66] An alternative way

X=[3.5 6.3, 33]

X is a 1X3 matrix with elements 3.5 ,

6.3 and 33. Commas or space areused to separate the elements in a row

Y=[1

4 ]

Y is a 2X1 matrix whose elements are 1

and 4.

Y = [ 1 ; 4] Semicolon are used to indicate the endof the row.

A=1:5 Equivalent to A=[1 2 3 4 5]


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MATLAB Statements

10

01V

MATLABStatement

Remarks

V=[ 2 3 5

3 3 8]

C=[1:3:11] C=[1 4 7 10]

Z=4\8 Z=2

Y=eye(2)

W = zeros(2,4)

833

532V

000

000V


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Polynomialsroots(p) Find the roots of a polynomial

whose coefficients are given in p

roots([1 4 2.1]) Find the roots of x2+4x+2.1=0

polyval(p,v) Evaluate the polynomial whose

coefficients are given in p at x=v

M t i


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Matrices

a vector x = [1 2 5 1]

x =

1 2 5 1

a matrix x = [1 2 3; 5 1 4; 3 2 -1]

x =

1 2 3

5 1 4

3 2 -1

transpose y = x. y =

1

2

5

1


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Matrices

x(i,j) subscription

whole row

whole column

y=x(2,3)

y =

4

y=x(3,:)

y =

3 2 -1

y=x(:,2)

y =

2

1

2


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Operators (arithmetic)

+ addition

- subtraction

* multiplication

/ division

^ power

complex

conjugate

transpose

.* element-by-element mult

./ element-by-element div

.^ element-by-element power

. transpose


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Logical Operators

> Greater than

>= Greater than or equal

< Less than


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Logical Operators

& AND

| OR

~ NOT

if (X>6) |(x


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Generating Vectors from

functions zeros(M,N) MxN matrix

of zeros

ones(M,N) MxN matrix

of ones

rand(M,N) MxN matrix

of uniformly distributedrandom numbers

on (0,1)

x = zeros(1,3)

x =

0 0 0

x = ones(1,3)

x =

1 1 1

x = rand(1,3)

x =0.9501 0.2311

0.6068


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Operators

[ ] concatenation

( ) subscription

x = [ zeros(1,3) ones(1,2) ]

x =

0 0 0 1 1

x = [ 1 3 5 7 9]x =

1 3 5 7 9

y = x(2)

y =

3

y = x(2:4)

y =

3 5 7


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Matlab Graphics

x = 0:pi/100:2*pi;

y = sin(x);

plot(x,y)

xlabel('x = 0:2\pi')

ylabel('Sine of x')

title('Plot of theSine Function')


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Multiple Graphs

t = 0:pi/100:2*pi;

y1=sin(t);

y2=sin(t+pi/2);

plot(t,y1,t,y2)grid on


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Multiple Plots

t = 0:pi/100:2*pi;

y1=sin(t);

y2=sin(t+pi/2);

subplot(2,2,1)plot(t,y1)

subplot(2,2,2)

plot(t,y2)


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Graph Functions (summary)

plot linear plot

stem discrete plot

grid add grid lines

xlabel add X-axis label

ylabel add Y-axis label

title add graph title

subplot divide figure window figure create new figure window

pause wait for user response


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Math Functions

Elementary functions (sin, cos, sqrt, abs, exp, log10, round)

type help elfun

Advanced functions (bessel, beta, gamma, erf)

type help specfun

type help elmat


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Functions Files

function f=myfunction(x,y)

f=x+y;

save it in myfunction.m

call it with y=myfunction(x,y)


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Function Files

A function file (called an M-file) is a text (ASCII) filethat contains a MATLAB function and, optionally,comments

The file is saved with the function name having usualMATLAB script file extension .m

A MATLAB function may be called from thecommand line or from any other M-file

When the function is called, it is executed, and controlis returned to the MATLAB workspace

Any values to be returned must be specified in thefunction syntax

function [out1, out2, ...] = myfun_name (in1, in2, ...)


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Example of a Function File

Create an M-file and save as swap.m

function [ a , b ] = swap ( a , b )

% These are comments

% the function swap receives two values a, b in the ( )

% swaps them, and returns the result in a, b in the [ ]

% the file is saved as swap.m

temp=a;

a=b;

b=temp;


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Example of a Function File

To use the function swap a MATLAB program could

assign values to two variables and then call the

function to swap them.>> x=5;>> y=6;

>> [ x, y ] = swap(x, y)

x =

6y =

5


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Flow Controlif A > B

'greater'

elseif A < B

'less'

else

'equal'

end

for x = 1:10

r(x) = x;

end

if statement

switch statement

for loops

while loops

continue statement

break statement


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if/elseif /else Statement

>> A = 2; B = 3;

>> if A > B

'A is bigger'

elseif A < B

'B is bigger'

elseif A == B

'A equals B'

else

error ('Something odd is happening')

end

ans =

B is bigger


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for loops

General form:for index=initial:

increment: limit

statements

end

s=0

for i=1:3:11

s=s+i

end


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for Loop

>> for i = 2:5

for j = 3:6

a(i, j) = (i + j)^2

end

end

>> a

a =

0 0 0 0 0 0

0 0 25 36 49 64

0 0 36 49 64 81

0 0 49 64 81 100

0 0 64 81 100 121


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switch Statement>> n = 8;

>> switch (rem(n,3))

case 0

m = 'no remainder'

case 1m = the remainder is one'

case 2

m = the remainder is two'

otherwiseerror ('not possible')

end

m =

the remainder is two


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while Loop

>> b = 4; a = 2.1; count =0;

>> while b - a > 0.01

a = a + 0.001;

count = count + 1;

end

>> countcount =

1891


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Miscellaneous

Loading data from a file

load myfile.dat

Suppressing Output

x = [1 2 5 1];

Random Numbers


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Random Numbers

x=rand(100,1);

stem(x);

hist(x,100)


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Coin Tosses

Simulate the outcomes of 1000 biased coin

tosses with p[Head]=0.4

x=rand(1000,1);p=sum(x


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Help

A good idea is use the help

help provides information about the availablefunctions and how to use them.

Tryhelp eig

help inv

help roots


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Getting Help

Using the Help Browser (.html, .pdf)

View getstart.pdf, graphg.pdf, using_ml.pdf

Type help

help function, e.g. help plot

Running demos

type demos

type help demos


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Thank You

Documents

MATLAB-Introduction to Applications