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School of Electrical Engineering and Computer Science

Digital Signal Processing: Lab Experiments

LAB 01: Getting Started with MATLAB

The Command window

You can start MATLAB by double clicking on the MATLAB icon that should be on the desktop

of your computer. This brings up the window called the Command Window. This window

allows a user to enter simple commands. To clear the Command Window type clc and next press

the Enter or Return key. To perform a simple computations type a command and next press the

Enter or Return key. For instance,

s = 1 + 2 (1)

The output is shown in blue below,

s =

3

fun = sin(pi/4) (2)

fun =

0.7071

In the second example the trigonometric function sine and the constant are used. In MATLAB

they are named sin and pi, respectively.

Note that the results of these computations are saved in variables whose names are chosen by the

user. If they will be needed during your current MATLAB session, then you can obtain their

values typing their names and pressing the Enter or Return key. For instance,

s (3)

s =

3

Variable name begins with a letter, followed by letters, numbers or underscores. MATLAB Release 2008

recognizes only the first 63 characters of a variable name.

To close MATLAB type exit in the Command Window and next press Enter or Return key. A

second way to close your current MATLAB session is to select File in the MATLAB's toolbar

and next click on Exit MATLAB option. All unsaved information residing in the MATLAB

Workspace will be lost.

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Numbers in MATLAB

There are three kinds of numbers used in MATLAB: integers real numbers complex numbersIntegers are entered without the decimal point

xi = 10 (4)

xi =

10

However, the following number

xr = 10.01 (5)

xr =

10.0100

is saved as the real number. Variables realmin and realmax denote the smallest and the largest positive

real numbers inMATLAB. For instance,

realmin (6)

ans =

2.2251e-308

Complex numbers in MATLAB are represented in rectangular form. The imaginary unit -1 is

denoted either by i orj

i (7)

ans =

0 + 1.0000i

In addition to classes of numbers mentioned above, MATLAB has three variables representing

the nonnumbers:

-Inf Inf NaNTheInfand Infare the IEEE representations for the negative and positive infinity, respectively.

Infinity is generated by overflow or by the operation of dividing by zero. The NaN stands for the

not-a-numberand is obtained as a result of the mathematically undefined operations such as

0.0/0.0 or -

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Workspace in MATLAB

All variables used in the current MATLAB session are saved in the Workspace. You can viewthe content of the Workspace by typing whos in the Command Window. For instance,

whos (8)

Name Size Bytes Class Attributes

ans 1x1 16 double complex

fun 1x1 8 double

s 1x1 8 double

xi 1x1 8 double

xr 1x1 8 double

shows all variables used in current session.

MATLAB HELP

One of the nice features of MATLAB is its help system. To learn more about a function you are

to use, say abs, type in the Command Window

help abs (9)

ABS Absolute value.ABS(X) is the absolute value of the elements of X. When

X is complex, ABS(X) is the complex modulus (magnitude) of

the elements of X.

See also sign, angle, unwrap, hypot.

Overloaded methods:

frd/abs

distributed/abs

iddata/abs

sym/abs

Reference page in Help browser

doc abs

If you do not remember the exact name of a function you want to learn more about use command

lookfor followed by the incomplete name of a function in the Command Window.

Now in the command window type

Help colon (9a)

Make sure you understand how the colon operator works

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To enter a statement that is too long to be typed in one line, use three periods, , followed by

Enter or Return. For instance,

x = sin(1) - sin(2) + sin(3) - sin(4) + sin(5) -...

sin(6) + sin(7) - sin(8) + sin(9) - sin(10) (9b)x =

0.7744

You can suppress output to the screen by adding a semicolon after the statement

u = 2 + 3; (9c)

MATLAB as a calculatorList of basic arithmetic operations in MATLAB include

Operation Symbol

addition +

subtraction -

multiplication *

division /

exponentiation ^

Observe the output of the following expressions

pi*pi 10 (8)

sin(pi/4) (9)ans 2 %

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(a) Make sure that you understand the colon notation. In particular, explain in words what thefollowing MATLAB code will produce

jkl = 0 : 6 (22) jkl = 2 : 4 : 17 (23)

jkl = 99 : -1 : 88 (24)

ttt = 2 : (1/9) : 4 (25)

tpi = pi * [ 0:0.1:2 ]; (26)

(b) Extracting and/or inserting numbers into a vector is very easy to do. Consider the followingdefinitionof xx:

xx = [ zeros(1,3), linspace(0,1,5), ones(1,4) ] (27)

xx(4:6) (28)

size(xx) (29)length(xx) (30)

xx(2:2:length(xx)) (31)

Explain the results echoed from the last four lines of the above code.

(c) Observe the result of the following assignments:yy = xx; yy(4:6) = pi*(1:3) (32)

EXERCISE 1:

Now write a statement that will take the vector xx defined in part (b) and replace the even indexed

elements (i.e., xx(2), xx(4), etc) with the constant (pi raised to the power pi). Use a vector

replacement, not a loop.

End of Exercise 1

Experiment with vectors in MATLAB. Think of the vector as a set of numbers. Try the following:

xk = cos( pi*(0:11)/4 ) %

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yy = [ ]; %

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Exercise 4

Generate a time vector (tt) to cover a range of t that will exhibit approximately two cycles of the

4000 Hz sinusoid. Use a definition for tt similar to that in Exercise 3. If we use T to denote the period of

the sinusoids, define the starting time of the vector tt to be equal to T, and the ending time as +T. Thenthe two cycles will include t = 0. Finally, make sure that you have at least 25 samples per period of the

sinusoidal wave. In other words, when you use the colon operator to define the time vector, make the

increment small enough to generate 25 samples per period.

Make a plot of both signals over the range of T t T. You may use arbitrary amplitude and phase for

generating the 4000 Hz sinusoid.

End of Exercise 4

IMPORTANT1. You must show completed exercises to the instructor during lab time and get the

attached sheet signed by the instructor. Submit the sheet to the instructor before

leaving.

2. A report of this lab will be due at the start of next lab. Include a discussion of theexercises in the report.

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INSTRUCTOR VERIFICATION SHEET

LAB number:___________________ Date of LAB:______________

Class: __________ Section:________

Name:________________________________ Reg #:____________

Name:________________________________ Reg #:____________

Name:________________________________ Reg #:____________

Exercise 1:

Verified:_______________________________ Date/Time:_______________

Exercise 2:


Exercise 3:


Exercise 4:


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