# An Introduction to MatLab by dfhdhdhdhjr

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```									An Introduction to
MATLAB

ELG3506
What is MATLAB ?
• The name MATLAB is an abbreviation for
MATrix LABoratory.
• In its early years (1970), MATLAB was a
matrix-based program for scientific and
engineering calculations.
• Today, MATLAB is much more than a
matrix-based program. It is a powerful
computer program for doing numerical
computations with vectors and arrays.
What is MATLAB ? (Cont‟d)
• It is both an environment and a programming
language, which gives it its great strength.
• MATLAB is also very useful for representing
information and data graphically in 2D and 3D.
• MATLAB has many toolboxes, which are a
collection of useful functions for specific classes
of problems. Some of these toolboxes are:
controls, signal processing and image
processing, radio frequency, filter design just to
name a few.
The MATLAB Interface
• There are two important windows on the
MATLAB interface,
• The “Command Window”, where you enter the
command at the prompt (>>) and,
• The “Workspace”, where all variables, arrays,
matrices and vectors are temporally saved.
• Programs or scripts can also be written and
executed in a single file called “M-File”.
The MATLAB Interface (Cont‟d)
The M-File

* Adding a semi-colon at the end of a command, tells MATLAB not to print
the results of the operations to the command screen.
The M-File (Cont‟d)
To open the editor and create a
new M-File, select,
New
M-File
MATLAB Syntax*
Variables
Variables are defined with the assignment operator, “=“. Values can come from
constants, from computation involving values of other variables, or from the
output of a function. For example:

* Some content taken from Wikipedia (http://en.wikipedia.org/wiki/MATLAB)
MATLAB Syntax (Cont‟d)
Vectors / Matrices
In MATLAB, a vector refers to a one dimensional (1×N or N×1) matrix. A matrix generally refers to a
multi-dimensional matrix, that is, a matrix with more than one dimension, for instance, an N×M, an
N×M×L, etc., where N, M, and L are greater than 1.
Basic Scalar Arithmetic
• The basic arithmetic operators applied to
scalars are +, -, * (multiplication), /
(division) & ^ for powers.
Where the constant „pi‟ is equal
to 3.1416‟
Matrix, Vector and Array Arithmetic
•   The Operators are +, -, *, /, ^, and ' .
•   MATLAB has two different types of arithmetic operations.
1. Matrix arithmetic operations are defined by the rules
of linear algebra.
2. Array arithmetic operations are carried out element
by element, and can be used with multidimensional
arrays.
•   The period character (.) distinguishes the array
operations from the matrix operations.
•   However, since the matrix and array operations are the
same for addition and subtraction, the character pairs .+
and .- are not used.
Matrix, Vector and Array Arithmetic
A+B    Adds A and B. A and B must have the same size.

A-B    Subtracts B from A. A and B must have the same size.

A*B    Matrix multiplication. C = A*B is the linear algebraic product of the matrices A and B.

A.*B   Array multiplication. A.*B is the element-by-element product of the arrays A and B. A
and B must have the same size.
A/B    Slash or matrix right division.

A./B   Array right division. A./B is the matrix with elements A(i,j)/B(i,j). A and B must have the
same size
A^B    Matrix power. X^p is X to the power p, if p is a scalar.

A.^B   Array power. A.^B is the matrix with elements A(i,j) to the B(i,j) power. A and B must
have the same size.
A'     Matrix transpose. A' is the linear algebraic transpose of A. For complex matrices, this is
the complex conjugate transpose.
A.'    Array transpose. A.' is the array transpose of A. For complex matrices, this does not
involve conjugation.
Defining a Complex Number
>> z = a + bi or,
>> z = a + bj or,
>> z = a + i*b or,
>> z = complex(a,b) or,
>> z = Aexp(j*B)      or,
>> z = a + b*sqrt(-1)

Note: „i‟ and „j‟ must not be defined otherwise
Iteration Statements
(The „for‟ and „while‟ Loops)

For Loop             While Loop
Condition
Index

for j=1:4,               while n <= M
statements
statements           end
end
Some Built-In Functions
pi                          3.1415....
zeros(n,m)                  n×m matrix of zeros
eye(m)                      m×m identity matrix
ones(n,m)                   n×m matrix of ones
abs(z)                      absolute value of „z‟
angle(z)                    angle of „z‟
sqrt(x)                     square root, e.g. i=sqrt(-1)
real(z), imag(z)            real, imaginary parts of „z‟
conj(z)                     complex conjugate of „z‟
sin(x), cos(x), tan(x)      trigonometric functions
asin(y),acos(y), atan(y)    inverse trigonometric functions
sinh(x), cosh(x), tanh(x)   hyperbolic functions
exp(z)                      exponential function
log(x)                      natural logarithm
complex(a,b)                define complex number a+jb
Graphics in MATLAB
plot(x,y)                 linear plot of y versus x
grid on / off             turns grid lines on graphics screen on or off
title(‟text‟)             prints a title for the plot
xlabel(‟text‟)            prints a label for the x-axis
ylabel(‟text‟)            prints a label for the y-axis
axis([0, 1, -2, 2])       overrides' default limits for plotting
hold on                   superimpose all subsequent plots
hold off                  turns off a previous hold on
legend(„data1‟,‟data2‟)   include a legend for each data set
clf                       clear graphics screen
Graphics in MATLAB
Example 1
The following MATLAB code plots the incident, reflected and standing
waves on a transmission line for any reflection coefficient, Gamma.

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