Basics of matlab

By
ANIL MAURYA
ELECTRICAL & ELECTRONICS
ENGINEER
1

Topics
Introduction
MATLAB Environment
Getting Help
Variables
Vectors, Matrices, and Linear Algebra
Mathematical Functions and Applications
PlottingPlotting
Selection Programming
M-Files
User Defined Functions
Applications
Specific topics
2ANIL MAURYA Electrical & Electronics Engineer

Introduction
What is MATLAB ?
• MATLAB is a computer program that combines computation and
visualization power that makes it particularly useful tool for
engineers.
• MATLAB is an executive program, and a script can be made with a
list of MATLAB commands like other programming language.
3
MATLAB Stands forMATLAB Stands for MATMATrixrix LABLABoratoryoratory..
•• The system was designed to make matrix computation particularlyThe system was designed to make matrix computation particularly
easy.easy.
The MATLAB environment allows the user to:
• manage variables
• import and export data
• perform calculations
• generate plots
• develop and manage files for use with MATLAB.
ANIL MAURYA Electrical & Electronics Engineer

MATLAB
Environment
To start MATLAB:
STARTSTART
PROGRAMS
MATLAB 7.0
MATLAB 7.0

Display Windows

Display Windows (con’t…)
Graphic (Figure) Window
Displays plots and graphs
Created in response to graphics commands.
M-file editor/debugger windowM-file editor/debugger window
Create and edit scripts of commands called M-files.

Getting Help
Type one of following commands in the command
window:
help – lists all the help topic
help topic – provides help for the specified topic
help command – provides help for the specified commandhelp command – provides help for the specified command
help help – provides information on use of the help command
helpwin – opens a separate help window for navigation
lookfor keyword – Search all M-files for keyword
PWD prints working directory

Getting Help (con’t…)
Google “MATLAB helpdesk”
Go to the online HelpDesk provided by
www.mathworks.com
8
You can find EVERYTHING you
need to know about MATLAB
from the online HelpDesk.

Variables
Variable names:
Must start with a letter
May contain only letters, digits, and the underscore “_”
Matlab is case sensitive, i.e. one & OnE are different variables.
Matlab only recognizes the first 31 characters in a variable name.
Assignment statement:Assignment statement:
Variable = number;
Variable = expression;
Example:
>> tutorial = 1234;
>> tutorial = 1234
tutorial =
1234
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NOTE: when a semi-colon
”;” is placed at the end of
each command, the result
is not displayed.

Variables (con’t…)
Special variables:
ans : default variable name for the result
pi: π = 3.1415926…………
eps: ∈ = 2.2204e-016, smallest amount by which 2 numbers can differ.
Inf or inf : ∞, infinity
NaN or nan: not-a-number
Commands involving variables:
who: lists the names of defined variables
whos: lists the names and sizes of defined variables
clear: clears all varialbes, reset the default values of special
variables.
clear name: clears the variable name
clc: clears the command window
clf: clears the current figure and the graph window.

Vectors, Matrices and Linear Algebra
Vectors
Array Operations
Matrices
Solutions to Systems of Linear Equations.

Vectors
A row vector in MATLAB can be created by an explicit list, starting with a left bracket,
entering the values separated by spaces (or commas) and closing the vector with a right
bracket.
A column vector can be created the same way, and the rows are separated by semicolons.
Example:
>> x = [ 0 0.25*pi 0.5*pi 0.75*pi pi ]
x =x =
0 0.7854 1.5708 2.3562 3.1416
>> y = [ 0; 0.25*pi; 0.5*pi; 0.75*pi; pi ]
y =
0
0.7854
1.5708
2.3562
3.1416
13
x is a row vector.
y is a column vector.

Vectors (con’t…)
Some useful commands:
x = start:endx = start:end create row vector x starting with start, counting bycreate row vector x starting with start, counting by
one, ending at endone, ending at end
x = start:increment:endx = start:increment:end create row vector x starting with start, counting bycreate row vector x starting with start, counting by
increment, ending at or before endincrement, ending at or before end
create row vector x starting with start, ending atcreate row vector x starting with start, ending at
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linspace(start,end,number)linspace(start,end,number) create row vector x starting with start, ending atcreate row vector x starting with start, ending at
end, having number elementsend, having number elements
length(x)length(x) returns the length of vector xreturns the length of vector x
y = x’y = x’ transpose of vector xtranspose of vector x
dot (x, y)dot (x, y) returns the scalar dot product of the vector x and y.returns the scalar dot product of the vector x and y.

Vectors (con’t…)
Vector Addressing – A vector element is addressed in MATLAB with an integer
index enclosed in parentheses.
Example:
>> x(3)
ans =
1.5708 3rd element of vector x1.5708
17
1st to 3rd elements of vector x
The colon notation may be used to address a block of elements.The colon notation may be used to address a block of elements.
(start : increment : end)(start : increment : end)
start is the starting index, increment is the amount to add to each successive index, and endstart is the starting index, increment is the amount to add to each successive index, and end
is the ending index. A shortened format (start : end) may be used if increment is 1.is the ending index. A shortened format (start : end) may be used if increment is 1.
Example:Example:
>> x(1:3)>> x(1:3)
ans =ans =
0 0.7854 1.57080 0.7854 1.5708
NOTE: MATLAB index starts at 1.
3rd element of vector x

Array Operations
Scalar-Array Mathematics
For addition, subtraction, multiplication, and division of an array
by a scalar simply apply the operations to all elements of the array.
Example:
>> f = [ 1 2; 3 4]
f =
1 21 2
3 4
>> g = 2*f – 1
g =
1 3
5 7
18
Each element in the array f is
multiplied by 2, then subtracted
by 1.

Array Operations (con’t…)
Element-by-Element Array-Array Mathematics.
OperationOperation Algebraic FormAlgebraic Form MATLABMATLAB
AdditionAddition a + ba + b a + ba + b
SubtractionSubtraction aa –– bb aa –– bb
MultiplicationMultiplication a x ba x b a .* ba .* b
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MultiplicationMultiplication a x ba x b a .* ba .* b
DivisionDivision aa ÷÷ bb a ./ ba ./ b
ExponentiationExponentiation aabb a .^ ba .^ b
Example:Example:
>> x = [ 1 2 3 ];>> x = [ 1 2 3 ];
>> y = [ 4 5 6 ];>> y = [ 4 5 6 ];
>> z = x .* y>> z = x .* y
z =z =
4 10 184 10 18
Each element in x is multiplied by
the corresponding element in y.

Matrices
A Matrix array is two-dimensional, having both multiple rows and multiple columns,
similar to vector arrays:
it begins with [, and end with ]
spaces or commas are used to separate elements in a row
semicolon or enter is used to separate rows.
A is an m x n matrix.
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•Example:
>> f = [ 1 2 3; 4 5 6]
f =
1 2 3
4 5 6
>> h = [ 2 4 6
1 3 5]
h =
2 4 6
1 3 5
the main diagonal

Matrices (con’t…)
Matrix Addressing:
-- matrixname(row, column)
-- colon may be used in place of a row or column reference to
select the entire row or column.
recall:
Example:
21
recall:
f =
1 2 3
4 5 6
h =
2 4 6
1 3 5
Example:
>> f(2,3)
ans =
6
>> h(:,1)
ans =
2
1

Some useful commands:
zeros(n)
zeros(m,n)
ones(n)
returns a n x n matrix of zeros
returns a m x n matrix of zeros
returns a n x n matrix of ones
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ones(n)
ones(m,n)
size (A)
length(A)
returns a n x n matrix of ones
returns a m x n matrix of ones
for a m x n matrix A, returns the row vector [m,n]
containing the number of rows and columns in
matrix.
returns the larger of the number of rows or
columns in A.

TransposeTranspose B = A’B = A’
Identity MatrixIdentity Matrix eye(n)eye(n) returns an n x n identity matrixreturns an n x n identity matrix
eye(m,n)eye(m,n) returns an m x n matrix with ones on the mainreturns an m x n matrix with ones on the main
diagonal and zeros elsewhere.diagonal and zeros elsewhere.
Addition and subtractionAddition and subtraction C = A + BC = A + B
more commands
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Addition and subtractionAddition and subtraction C = A + BC = A + B
C = AC = A –– BB
Scalar MultiplicationScalar Multiplication B =B = ααA, whereA, where αα is a scalar.is a scalar.
Matrix MultiplicationMatrix Multiplication C = A*BC = A*B
Matrix InverseMatrix Inverse B = inv(A), A must be a square matrix in this case.B = inv(A), A must be a square matrix in this case.
rank (A)rank (A) returns the rank of the matrix A.returns the rank of the matrix A.
Matrix PowersMatrix Powers B = A.^2B = A.^2 squares each element in the matrixsquares each element in the matrix
C = A * AC = A * A computes A*A, and A must be a square matrix.computes A*A, and A must be a square matrix.
DeterminantDeterminant det (A), and A must be a square matrix.det (A), and A must be a square matrix.
A, B, C are matrices, and m, n, α are scalars.

Solutions to Systems of Linear Equations
Example: a system of 3 linear equations with 3 unknowns (x1, x2, x3):
3x1 + 2x2 – x3 = 10
-x1 + 3x2 + 2x3 = 5
x1 – x2 – x3 = -1
 −123 x 10
Let :
24
Then, the system can be described as:
Ax = b










−−
−
−
=
111
231
123
A










=
3
2
1
x
x
x
x










−
=
1
5
10
b

Solutions to Systems of Linear Equations (con’t…)
Solution by Matrix Inverse:
Ax = b
A-1Ax = A-1b
x = A-1b
MATLAB:
>> A = [ 3 2 -1; -1 3 2; 1 -1 -1];
Solution by Matrix Division:Solution by Matrix Division:
The solution to the equationThe solution to the equation
Ax = bAx = b
can be computed usingcan be computed using left divisionleft division..
MATLAB:
>> A = [ 3 2 -1; -1 3 2; 1 -1 -1];>> A = [ 3 2 -1; -1 3 2; 1 -1 -1];
>> b = [ 10; 5; -1];
>> x = inv(A)*b
x =
-2.0000
5.0000
-6.0000
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Answer:
x1 = -2, x2 = 5, x3 = -6
Answer:
x1 = -2, x2 = 5, x3 = -6
NOTE:
left division: Ab b ÷ A right division: x/y x ÷ y
>> A = [ 3 2 -1; -1 3 2; 1 -1 -1];
>> b = [ 10; 5; -1];
>> x = Ab
x =
-2.0000
5.0000
-6.0000

Basics of matlab

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