Introduction to MATLAB

Introduction to MATLAB

MATLAB is a software package for high performance numerical computation and visualization provides an interactive environment with hundreds of built in functions for technical computation, graphics and animation. The MATLAB name stands for MATrix Laboratory

The diagram shows the main features and capabilities of MATLAB.

At its core, MATLAB is essentially a set (a “toolbox”) of routines (called “m files” or “mex files”) that sit on your computer and a window that allows you to create new variables with names (e.g. voltage and time) and process those variables with any of those routines (e.g. plot voltage against time, find the largest voltage, etc).

It also allows you to put a list of your processing requests together in a file and save that combined list with a name so that you can run all of those commands in the same order at some later time. Furthermore, it allows you to run such lists of commands such that you pass in data and/or get data back out (i.e. the list of commands is like a function in most programming languages). Once you save a function, it becomes part of your toolbox (i.e. it now looks to you as if it were part of the basic toolbox that you started with).

For those with computer programming backgrounds: Note that MATLAB runs as an interpretive language (like the old BASIC). That is, it does not need to be compiled. It simply reads through each line of the function, executes it, and then goes on to the next line. (In practice, a form of compilation occurs when you first run a function, so that it can run faster the next time you run it.)

MATLAB Windows:

MATLAB works with through three basic windows

Command Window : This is the main window .it is characterized by MATLAB command prompt >> when you launch the application program MATLAB puts you in this window all commands including those for user-written programs ,are typed in this window at the MATLAB prompt

Graphics window: the output of all graphics commands typed in the command window are flushed to the graphics or figure window, a separate gray window with white background color the user can create as many windows as the system memory will allow

Edit window: This is where you write edit, create and save your own programs in files called M files.

Input-output:

MATLAB supports interactive computation taking the input from the screen and flushing, the output to the screen. In addition, it can read input files and write output files

Data Type: the fundamental data –type in MATLAB is the array. It encompasses several distinct data objects- integers, real numbers, matrices, character strings, structures and cells. There is no need to declare variables as real or complex, MATLAB automatically sets the variable to be real.

Dimensioning: Dimensioning is automatic in MATLAB. No dimension statements are required for vectors or arrays. we can find the dimensions of an existing matrix or a vector with the size and length commands.

Basic Instructions in Mat lab

1. T = 0: 1:10

This instruction indicates a vector T which as initial value 0 and final value 10 with an increment of 1

Therefore T = [0 1 2 3 4 5 6 7 8 9 10]

2. F= 20: 1: 100

Therefore F = [20 21 22 23 24 ……… 100]

3. T= 0:1/pi: 1

Therefore T= [0, 0.3183, 0.6366, 0.9549]

4. zeros (1, 3)

The above instruction creates a vector of one row and three columns whose values are zero

Output= [0 0 0]

5. zeros( 2,4)
Output =	0 0 0 0
	0 0 0 0

6. ones (5,2)

The above instruction creates a vector of five rows and two columns

Output =	1 1
	1 1
	1 1

1 1

1 1

7. a = [ 1 2 3]

b = [4 5 6]

a.*b = [4 10 18]

Which is multiplication of individual elements?

i.e. [4X1 5X2 6X3]

8    if  C= [2 2 2]

b.*C results in [8 10 12]

9. plot (t, x)

If	x = [6 7 8 9]
	t = [1 2 3 4]

This instruction will display a figure window which indicates the plot of x versus t

10. stem (t,x)

This instruction will display a figure window as shown

11. Subplot: This function divides the figure window into rows and columns

Subplot (2 2 1) divides the figure window into 2 rows and 2 columns 1 represent number of the figure

1 (2 2 1)	2 (2,2,2)
3 (2 2 3)	4 (2 2 4)

Subplot (3, 1, 3)

1 (3,1,1)

2 (3,1,2)

3 (3,1,3)

12. Filter

Syntax:      y = filter(b,a,X)

Description: y = filter(b,a,X) filters the data in vector X with the filter described by numerator coefficient vector b and denominator coefficient vector a.If a(1) is not equal to 1, filter normalizes the filter coefficients by a(1). If a(1) equals 0, filter returns an error.

13. Impz

Syntax: [h,t] = impz(b,a,n)

Description: [h,t] = impz(b,a,n) computes the impulse response of the filter with numerator coefficients b and denominator coefficients a and computes n samples of the impulse response when n is an integer (t = [0:n-1]'). If n is a vector of integers, impz computes the impulse response at those integer locations, starting the response computation from 0 (and t = n or t = [0 n]). If, instead of n, you include the empty vector [] for the second argument, the number of samples is computed automatically by default.

14. Fliplr

Syntax: B = fliplr(A)

Description: B = fliplr(A) returns A with columns flipped in the left-right direction, that is, about a vertical axis.If A is a row vector, then fliplr(A) returns a vector of the same length with the order of its elements reversed. If A is a column vector, then fliplr(A) simply returns A.

15. Conv

Syntax: w = conv(u,v)

Description: w = conv(u,v) convolves vectors u and v. Algebraically, convolution is the same operation as multiplying the polynomials whose coefficients are the elements of u and v.

16.Disp

Syntax: disp(X)

Description: disp(X) displays an array, without printing the array name. If X contains a text string, the string is displayed.Another way to display an array on the screen is to type its name, but this prints a leading "X=," which is not always desirable.Note that disp does not display empty arrays.

17.xlabel

Syntax: xlabel('string')

Description: xlabel('string') labels the x-axis of the current axes.

18. ylabel

Syntax : ylabel('string')

Description: ylabel('string')   labels the y-axis of the current axes.

19.Title

Syntax : title('string')

Description: title('string') outputs the string at the top and in the center of the current axes.

20.grid on

Syntax : grid on

Description: grid on adds major grid lines to the current axes.

Procedure to program in MATLAB:

1 .  Open Matlab 2.  Open New M-File 3. Type the program 4. Save in current directory 5. Compile and run the program 6. For Output See Command/Figure Window.