lecture on introduction to matlab

8/3/2019 Lecture on Introduction to MATLAB

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An Introduction to MATLABLesson 1

Mani MOHAN

CE407

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MATLAB MATLAB==MATrix LABratory

It is widely used to solve different types ofscientific problems.

The basic data structure is a complex doubleprecision matrix.

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Run MATLABFrom Start Menu

Select MATLAB

MATLAB PromptTells that MATLAB

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s rea y or yourcommand


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MATLAB Layout1 to 5 different windows can be selected to appear (View)

Current

directorywindow

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Commandwindow

CommandHistorywindow


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MATLAB shortcutsHelpSIMULINKOpen filesNew

file

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MATLAB AS A CALCULATOR

>> 39*4.4+5

ans =176.6000

Command window

The MATLAB command

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omman w n ow

The result.


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MATLAB Variable names:

Starts with a letter

Up to 31 characters ( some use 19 or 21)

May contain letters, digits and underscore_ Case sensitive (A is not the same as a)

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MATLAB Assignment Variable names:

A=2.3A =

The MATLAB command

Up to 31 characters ( some use 19 or 21)

May contain letters, digits and underscore_

Case sensitive (A is not the same as a)

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.

This is the result of theMATLAB statement


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Scalar Assignment

A=2.3

A=[2.3]

The square braces [ ] areused to define matrices.

and set its value to 2.3A =

2.3000

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=

2.3000

We can use them forscalars too.


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Row vectorThe square braces are

X=[2,3 7 ] Space or comma areused to separate

use o e ne a ma r x

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2 3 7


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Column vectorThe square braces are

X=[2;3 ; 7 ]

use o e ne a ma r x

semicolon are used to end arow.

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2

3

7

ou can a so use oend a row


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MATLAB StatementsMATLAB Statement Remarks

=5.66 s a sca ar

C=[5.66] An alternative way

X=[3.5 6.3, 33]X is a 1X3 matrix with elements 3.5 , 6.3and 33. Commas or space are used toseparate the elements in a row

Y=[1 Y is a 2X1 matrix whose elements are 1

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4 ]

an 4.

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

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


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MATLAB StatementsMATLAB Statement Remarks

=

01

V=[ 2 3 5

3 3 8]

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

Z=4\8 Z=2

Y=eye(2)

=

833

532V

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10

W = zeros(2,3)

=

000

000V


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Polynomialsroots(p) Find the roots of a

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

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given in p at x=v


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Help A good idea is use the help

help provides information about theavailable functions and how to use them.

Tr

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help eighelp inv

help roots


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Programming in MATLAB There are two types of MATLAB programs

% script file

P=[1 3 2]

function [y]=fun(x)

y=x^2+3*x^2+2

script files function files

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Programming in MATLAB

Script files

A Script file contains a set of MATLAB

command Use them when you have a long sequence of

statements to solve a problem Can run the program by typing its name in

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editor window.


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Logical Operators> Greater than

>= Greater than or equal

< Less than


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Logical Operators& AND

| OR

~ NOT

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if (X>6) |(x


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If structures

General form: If (x>0)

If condition

statements

elsestatements

sign=1

elseif (x==0)

sign=0

else

sign=-1

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enen


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for loops

for index=initial: increment: limit

statements

end

s=0

for i=1:3:11

s=s+i

end

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Example MATLAB program to find the roots of

% program 1 performs four iterations of

% Newtons Method

X=.7

X =1.1111

X =1.0483

X =

Result

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for i=1:4X=X (2*cos(X)-1)/(-2*sin(X))

end

1.0472X =

1.0472

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