Introduction to MATLAB.pptx

MATLAB

MATRIX stands for MATrix LABoratory

The aim of education is to teach students how

Introduction

• _{MATLAB is a mathematical and graphical}

software package; it has numerical, graphical, and programming capabilities. It has built-in functions to do many operations, and there are toolboxes that can be added to augment these functions (e.g., for signal processing). There are versions available for different

• _{There are several commands that can serve as an} introduction to MATLAB and allow you to get help: • _{info will display contact information for the}

product;

• _{demo has demos of several options in MATLAB;} • _{help will explain any command;}

Starting MATLAB

• _{You can enter MATLAB by double-clicking on the MATLAB} shortcut icon on your Windows desktop. When you start

MATLAB, a special window called the MATLAB desktop appears. The desktop is a window that contains other windows. The

major tools within or accessible from the desktop are: • _{The Command Window}

• _{The Command History} • _{The Workspace}

• _{The Current Directory} • _{The Help Browser}

Quitting MATLAB

• _{To end your MATLAB session, type quit at the}

prompt in the Command Window, or select File → Exit MATLAB in the desktop main

Uses of MATLAB

• _{MATLAB is widely used as a computational tool in science}

and engineering encompassing the fields of physics,

chemistry, math and all engineering streams. It is used in a range of applications including:

• _{signal processing and communications} • _{image and video processing}

• _{control systems}

Creating variables in MATLAB

• The name must begin with a letter of the alphabet. After that, the name can contain letters, digits, and the underscore character (e.g., value_1), but it cannot have a space.

• There is a limit to the length of the name; the built-in function

namelengthmax tells how many characters this is.

• MATLAB is case-sensitive. That means that there is a difference between upper- and lowercase letters. So, variables called mynum, MYNUM, and

Mynum are all different.

• There are certain words called reserved words that cannot be used as variable names.

• _{MATLAB is case-sensitive. That means that}

there is a difference between upper- and

lowercase letters. So, variables called mynum, MYNUM, and Mynum are all different.

• _{There are also certain words called reserved}

Reserved or keywords of MATLAB

• _{The reserved words, called keywords, are:}

• _{Additionally, variable names should always be}

mnemonic, which means they should make some sense. For example, if the variable is storing the radius of a circle, a name such as “radius” would make sense as against a

Variables and assignment statements

• _{One easy way to create a variable is to use an assignment statement.} The format of an assignment statement is

• variablename = expression

• _{The variable is always on the left, followed by the assignment}

operator, = (unlike in mathematics, the single equal sign does not

mean equality), followed by an expression. The expression is evaluated and then that value is stored in the variable.

• _{For example, this is the way it would appear in the Command Window:} • _{>> mynum = 6}

• _{mynum =} • ₆

• _{Since the equal sign is the assignment operator, and does not} mean equality, the statement should be read as “mynum gets the value of 6” (not “mynum equals 6”).

• _{Note that the variable name must always be on the left, and the} expression on the right. An error will occur if these are reversed. • _{>> 6 = mynum}

• _{??? 6 = mynum} • _|

• _{Error: The expression to the left of the equals sign is not} • _{a valid target for an assignment.}

Assignment

• _{In MATLAB, variables must always have values}

before they are used.

• _{To create a variable in MATLAB, you declare it and}

assign an initial value to it. This initial value could be 0, 1, 1000, or whatever value it is supposed to be.

• _Examples: • _{>> x = 2;}

Examples of expressions

• _{rho = (1+sqrt(5))/2} • _{rho = 1.6180}

Commands that relate to variables

• _{The following commands relate to variables:}

• _{who shows variables that have been defined in this Command}

Window

• _{(this just shows the names of the variables)}

• _{whos shows variables that have been defined in this}

Command Window (this shows more information on the variables, similar to what is in the Workspace Window)

• _{clear clears out all variables so they no longer exist} • _{clear variablename clears out a particular variable}

• _{If nothing appears when who or whos is entered, that means}

Operators

• _Operators

• There are in general two kinds of operators: unary operators, which

operate on a single value or operand; and binary operators, which operate on two values or operands. The symbol “–”, for example, is both the unary operator for negation and the binary operator for subtraction.

• Here are some of the common operators that can be used with numeric expressions:

• + addition

• – negation, subtraction

• _{* multiplication}

• _{/ division (divided by e.g. 10/5 is 2)} • \ division (divided into e.g. 5\10 is 2)

Initializing, Incrementing, and Decrementing

• _{Frequently, values of variables change. Putting the}

first or initial value in a variable is called initializing

the variable.

• _{Adding to a variable is called incrementing. For}

example, the statement

• _{mynum = mynum + 1}

increments the variable mynum by 1. Likewise,

Operator precedence

• _{The order from highest to lowest are:} • _{() parentheses}

• _{^ exponentiation} • _{– negation}

MATLAB special variables

• _{pi Value of π}

• _{eps Smallest incremental number} • _{inf Infinity}

• _{NaN Not a number e.g. 0/0} • _{i and j, i = j = square root of -1}

MATLAB relational operators

• _{MATLAB supports six relational operators.} • _{Less Than <}

• _{Less Than or Equal to <=} • _{Greater Than >}

• _{Greater Than or Equal to >=} • _{Equal To ==}

• _{Not Equal To ~= (NOT; equivalent to != like in}

MATLAB logical operators

• _{MATLAB supports three logical operators.} • _{not ~ % highest precedence}

• _{When assignments are long, we can extend to}

another line by using an ellipsis (…). For example,

• _{initial_velocity = 0;} • _{acceleration = 9.8;} • _{time = 20;}

• _{Complex Numbers}

• _{MATLAB can work with complex numbers as easily as with real} numbers. For example, to find the roots of the quadratic

polynomial x2 _{+ 2x + 5 enter}

• _{>> a = 1; b = 2; c = 5;}

• _{>> x1 = ( -b + sqrt( b^2 - 4*a*c ) ) / (2*a)} • _{>> x2 = ( -b - sqrt( b^2 - 4*a*c ) ) / (2*a)} • _{The output is}

• _{-1.0000 + 2.0000i} • _and

• _{There are standard functions for obtaining the real}

part, the imaginary part, and the complex

conjugate of a complex number or variable. For example,

• _{>> x = 3 - 5i} • _{>> real(x)} • _{>> imag(x)} • _{>> conj(x)}

• _{1. Consider a triangle with sides a, b, and c and corresponding}

angles ab, ac, and bc.

• _{(a) Use the law of cosines, i.e.,} • _c2 _{= a}2 _{+ b}2 _{- 2ab cos ab;}

• _{to calculate c if a = 3.7, b = 5.7, and ab = 79⁰.} • _{(b) Then show c to its full accuracy.}

• _{(c) Use the law of sines, i.e.,} •

• _{= ,} •