Introduction to MATLAB

Introduction
to
MATLAB
(MATrix LABoratory)
Presented By:
Bhavesh Shah
Asst. Prof.,

Outline:
 What is MATLAB?
 MATLAB Screen
 Variables, array, matrix, indexing
 Operators (Arithmetic, relational, logical)
 Display Facilities
 Flow Control
 Writing User Defined Functions
 Design Neural Network(NN)
 Graphical User Interface (GUI)
 Image Processing Toolbox
 Advantages and Disadvantages of MATLAB
 Conclusion

MATLAB workshop under CSI Student
27-28 Sept,2012 Chapter 2

What is MATLAB?
The MATLAB is high-performance language for technical computing integrates
computation, visualization, and programming in an easy-to-use environment where
problems and solutions are expressed in familiar mathematical notation.

Where MATLAB is used

 Math and computation

 Algorithm development

 Data acquisition

 Modelling, simulation, and prototyping

 Data analysis, exploration, and visualization

 Scientific and engineering graphics

 Application development, including graphical user interface building


Toolboxes provided By MATLAB
1. Aerospace Simulation
2. Neural Network
3. Parallel Computing
4. Image Acquisition
5. Image processing
6. Genetic Algorithm
7. Fuzzy Logic
8. Database processing
9. Video and Image processing
10. Control System
11. Signal Processing
12. Statistics
13. Financial Toolbox
14. Curve fitting

MATLAB Screen
 Command Window
 type commands

 Current Directory
 View folders and m-files

 Workspace
 View program variables
 Double click on a variable
to see it in the Array Editor

 Command History
 view past commands
 save a whole session
using diary


Structure of MATLAB


Comment used in MATLAB
 “%” is the neglect sign for MATLAB (equivalent of
“//” in C). Anything after it on the same line is
neglected by MATLAB compiler.

 Sometimes slowing down the execution is done
deliberately for observation purposes. You can
use the command “pause” for this purpose

>>pause %wait until any key
>>pause(3) %wait 3 seconds


Useful Commands

 The two commands used most by Matlab
users are
>>help functionname

>>lookfor keyword


Variables
 No need for types. i.e.,

int a;
double b;
float c;

 All variables are created with double precision unless
specified and they are matrices.

>>x=5;
>>x1=2;

 After these statements, the variables are 1x1 matrices
with double precision.

Variables(cont…)

 Use meaningful names for variables
 MATLAB variable names
– must begin with a letter
– can contain any combination of letters, numbers and
underscore (_)
– must be unique in the first 31 characters
 MATLAB is case sensitive: “name”, “Name” and “NAME”
are considered different variables.
 Never use a variable with the same name as a MATLAB
command.
 Naming convention: use lowercase letters

Variable(cont…)

Initialization using shortcut statements
– colon operator “first:increment:last”
>> x = 1:2:10
x =1 3 5 7 9
>> y = 0:0.1:0.5
y = 0 0.1 0.2 0.3 0.4 0.5


Variable(cont…)


Array


Array, Matrix
 a vector x = [1 2 5 1]

x =
1 2 5 1

 a matrix x = [1 2 3; 5 1 4; 3 2 -1]

x =
1 2 3
5 1 4
3 2 -1

 transpose y = x’ y =
1
2
5
1


Long Array, Matrix
 t =1:10

t =
1 2 3 4 5 6 7 8 9 10
 k =2:-0.5:-1

k =
2 1.5 1 0.5 0 -0.5 -1

 B = [1:4; 5:8]

=
1 2 3 4
5 6 7 8


Built-in Variables

 pi: p value up to 15 significant digits
 i, j: sqrt(-1)
 Inf: infinity (such as division by 0)
 NaN: Not-a-Number (such as division of zero by zero).
 clock: current date and time as a vector
 date: current date as a string (e.g. 16-Feb-2004)
 eps: epsilon
 ans: default variable for answers
 tic…toc


Built-in Math function

 abs, sign
 log, log10, log2
 exp
 sqrt
 sin, cos, tan
 max, min
 round, floor, ceil, fix
 mod


Built in Functions

 sort
 sortrows
 mod(num,2)


Built in function related to String


Limit and Integration


Differentiation


Solving Equations

>> solve('cos(2*x)+sin(x)=1')


Some useful Command

 who: show your workspace
 whos: show your workspace with details
 memory: show memory status
 clc: clear command window
 clear: clear workspace variable
 cntl+d: forcefully quit
 diary: to maintain a log


Initializing with Built-in Functions

 zeros(n)
 zeros(n,m)
 zeros(size(arr))
 ones(n)
 ones(n,m)
 ones(size(arr))
 eye(n)
 eye(n,m)
 length(arr)
 size(arr)

Generating Vectors from functions
 zeros(M,N) MxN matrix of zeros x = zeros(1,3)
x =
0 0 0

 ones(M,N) MxN matrix of ones
x = ones(1,3)
x =
1 1 1
 rand(M,N) MxN matrix of uniformly
distributed random x = rand(1,3)
numbers on (0,1) x =
0.9501 0.2311 0.6068


Matrix Index
 The matrix indices begin from 1 (not 0 (as in C))
 The matrix indices must be positive integer
Given:

A(-2), A(0)

Error: ??? Subscript indices must either be real positive integers or logicals.

A(4,2)
Error: ??? Index exceeds matrix dimensions.

Concatenation of Matrices
 x = [1 2], y = [4 5], z=[ 0 0]

A = [ x y]

1 2 4 5

B = [x ; y]

1 2
4 5

C = [x y ;z]
Error:
??? Error using ==> vertcat CAT arguments dimensions are not consistent.


Operators (arithmetic)
+ addition
- subtraction
* multiplication
/ division
^ power
„ transpose


Matrices Operations

Given A and B:

Addition Subtraction Product Transpose


Operators (Element by Element)

.* : element-by-element multiplication
./ : element-by-element division
.^ : element-by-element power


The use of “.” – “Element” Operation
A = [1 2 3; 5 1 4; 3 2 1]
A=
1 2 3
5 1 4
3 2 -1

b = x .* y c=x./y d = x .^2
x = A(1,:) y = A(3 ,:)
b= c= d=
x= y= 3 8 -3 0.33 0.5 -3 1 4 9
1 2 3 3 4 -1
K= x^2
Error:
??? Error using ==> mpower Matrix must be square.
B=x*y
Error:
??? Error using ==> mtimes Inner matrix dimensions must agree.

Matrix Operation(cont…)

 transpose(„)
 tril: lower triangular matrix
 triu: upper triangular matrix
 rank: show rank of matrix
 det: determinant of matrix
 diag: returns principle diagonal
 inv: inverse of the matrix
 eig: eign value(matrix must be
square matrix)


Displaying Data/Text


Displaying Data/Text(cont…)


Import/Export Data from Command


Operators (relational, logical)

 == Equal to
 ~= Not equal to
 < Strictly smaller
 > Strictly greater
 <= Smaller than or equal to
 >= Greater than equal to
 & And operator
 | Or operator

Flow Control

 if
 for
 while
 break
 continue
 switch and case


Control Structures
Some Dummy Examples
 If Statement Syntax
if ((a>3) & (b==5))
Some Matlab Commands;
if (Condition_1) end
MATLAB Commands
if (a<3)
elseif (Condition_2) Some Matlab Commands;
MATLAB Commands elseif (b~=5)
elseif (Condition_3) Some Matlab Commands;
end
MATLAB Commands
else if (a<3)
MATLAB Commands else
end Some Matlab Commands;
end

Control Structures
Some Dummy Examples
 For loop syntax for i=1:100
for i=start: Last index Some Matlab Commands;
end
MATLAB Commands
end for j=1:3:200
end

for m=13:-0.2:-21
end

for k=[0.1 0.3 -13 12 7 -9.3]
end

Control Structures
Dummy Example
 While Loop Syntax while ((a>3) & (b==5))
end
while (condition) % while loop
i=1;
MATLAB Commands while(i<10)
disp(i);
end i=i+1;
end


Use of M-File
Click to create
a new M-File

• Extension “.m”
• A text file containing script or function or program to run

Switch and case


Continue statement


Break statement


Use of M-File Save file as Denem430.m

If you include “;” at the
end of each statement,
result will not be shown
immediately


Solution

>> A{1,1} = 'MATLAB ';
>> A{1,2} = 'SIMULINK ';
>> A = deblank(A)

A=

'MATLAB' 'SIMULINK'


Writing User Defined Functions

 Functions are m-files which can be executed by
specifying some inputs and supply some desired
outputs.
 The code telling the MATLAB that an m-file is actually
a function is

function out1=functionname(inp1)
function out1=functionname(inp1,inp2,inp3)
function [out1,out2]=functionname(inp1,inp2)

 You should write this command at the beginning of the
m-file and you should save the m-file with a file name
same as the function name

How to read a text file

fid = fopen('message.txt','r');
ice1= fread(fid);
s = char(ice1');
fclose(fid);
disp(s);

Ans hello


How to write a text file

txt=[65 67 68 69];
fid = fopen('output.txt','wb');
fwrite(fid,char(txt),'char');
fclose(fid);

ANS =ACDE


Writing User Defined Functions
 Examples
 Write a function : out=squarer (A, ind)

 Which takes the square of the input matrix if the input
indicator is equal to 1
 And takes the element by element square of the input
matrix if the input indicator is equal to 2

Same Name


Basic Task: Plot the function sin(x)
between 0≤x≤4π
 Create an x-array of 100 samples between 0
and 4π.
Syntax: linspace(start, interval, end);

>>x=linspace(0,4*pi,100);
 Calculate sin(.) of the x-array

>>y=sin(x);
 Plot the y-array
>>plot(y)


Plot the function e-x/3sin(x) between
0≤x≤4π
 Create an x-array of 100 samples between 0
and 4π.
>>x=linspace(0,4*pi,100);

 Calculate sin(.) of the x-array
>>y=sin(x);

 Calculate e-x/3 of the x-array
>>y1=exp(-x/3);

 Multiply the arrays y and y1
>>y2=y*y1;

Plot the function e-x/3sin(x) between
0≤x≤4π
 Multiply the arrays y and y1 correctly
>>y2=y.*y1;

 Plot the y2-array
0.7

>>plot(y2) 0.6

0.5

0.4

0.3

0.2

0.1

0

-0.1

-0.2

-0.3
0 10 20 30 40 50 60 70 80 90 100


Display Facilities

 plot(par1,par2) 0.7

0.6

0.5

Example: 0.4

>>x=linspace(0,4*pi,100); 0.3

>>y=sin(x);
0.2

0.1

>>plot(y) 0

>>plot(x,y) -0.1

-0.2

-0.3
0 10 20 30 40 50 60 70 80 90 100


Neural Network
(NN)


How to Design Neural Network

1. Collect data
2. Create the network
3. Configure the network
4. Initialize the weights and biases
5. Train the network
6. Validate the network
7. Use the network


Simple Neuron/1st layer Perceptron

b
X1 wb=1
w1
E
y

w2
X2


Transfer Function


Vectors used in NN


Neural Network Architecture


Multilayer NN


How to open Neural Network Tool

>>nftool


Graph Plot


Display Facilities

 title(.)
>>title(‘This is the sinus function’)
This is the sinus function
1

0.8

 xlabel(.) 0.6

0.4

>>xlabel(‘x (secs)’) 0.2

sin(x)
0

 ylabel(.) -0.2

-0.4

-0.6

-0.8
>>ylabel(‘sin(x)’) -1
0 10 20 30 40 50 60 70 80 90 100
x (secs)


GUI
(Graphical User Interface)


GUIDE

GUIDE is Graphical User Interface Development Environment, provides a
set of tools for creating graphical user interfaces (GUIs). These tools
simplify the process of laying out and programming GUIs.

To open GUI :
>> guide


DIALOG BOX

warndlg('hello'); helpdlg('hello'); errordlg('hello');

msgbox('hello');


USER INTERFACE GET FILE

[filename, pathname] = uigetfile('*.m', 'Pick an M-file');
if isequal(filename,0) | isequal(pathname,0)
disp('User pressed cancel')
else
disp(['User selected ', fullfile(pathname, filename)])
end


GUI…


PUSH BUTTON


TOGGLE BUTTON


RADIO BUTTON


CHECKBOX


EDIT TEXT


STATIC TEXT


SLIDER


FRAME


LISTBOX


POPUP MENU


AXES


ALIGN OBJECTS


MENU EDITOR


M FILE EDITOR


PROPERTY INSPECTOR


RUN


PUSH BUTTON


WRITE THE CODE BELOW THE
CALLBACK

a =imread('cameraman.tif');

imshow(a);


RUN THE PROGRAM OR PRESS F5


RIGHT CLICK PUSH BUTTON & GO FOR
PROPERTY INSPECTOR


CHOOSE AXES


RIGHT CLICK AXES & GO FOR
PROPERTY INSPECTOR


CHANGE THE STRING AND TAG
VALUE


CALLBACK

axes(handles.one);

imshow(a);


RUN THE PROGRAM


CODE


axes(handles.one);

imshow(a);


TOGGLE BUTTON


RIGHT CLICK TOGGLE & GO FOR
PROPERTY INSPECTOR


VALUE


RIGHT CLICK TOGGLE & GO FOR M
FILE EDITOR


CALLBACK

a=get(hObject,'Value');

if a ==1


axes(handles.one);

imshow(a);

else

a =imread('greens.jpg');

axes(handles.one);

imshow(a);

end


RUN THE PROGRAM


RIGHT CLICK CHECK BOX & GO FOR
PROPERTY INSPECTOR


VALUE


RIGHT CLICK CHECK BOX & GO FOR M
FILE EDITOR


CALLBACK


RUN THE PROGRAM


Image Processing


How to read an image

a =imread('cameraman.tif'); a =imread('flowers.tif');
imshow(a); imshow(a);
pixval on; pixval on;


NOISE AND FILTER

I = imread('eight.tif');
J = imnoise(I,'salt & pepper',0.02);
K = medfilt2(J);
subplot(1,2,1);imshow(J)
subplot(1,2,2);imshow(K)


How to read an audio file

a =wavread('test.wav');
wavplay(a,44100);
Plot(a);


How to read an video file

a=aviread('movie.avi');
movie(a);


Add two images

I = imread('rice.tif');
J = imread('cameraman.tif');
K = imadd(I,J,'uint16');
J = imadd(I,Irice50);
imshow(K,[])
subplot(1,2,1), imshow(I)
subplot(1,2,2), imshow(J)


Subtract two images

Iq = imsubtract(I,Irice50);
subplot(1,2,1), imshow(I)
subplot(1,2,2), imshow(Iq)


Convert image to gray and binary
clc;
clear;
close all
a= imread('flowers.tif');
subplot(2,2,1);
imshow(a);
subplot(2,2,2);
b=imresize(a,[256 256]);
imshow(b);
subplot(2,2,3);
c=rgb2gray(b);
imshow(c);
subplot(2,2,4);
d=im2bw(c);
imshow(d);


RGB component
a=imread('flowers.tif');
subplot(2,2,1);
imshow(a);
R=a;
G=a;
B=a;
R(:,:,2:3)=0;
subplot(2,2,2);
imshow(R);
G(:,:,1)=0;
G(:,:,3)=0;
subplot(2,2,3);
imshow(G);
B(:,:,1)=0;
B(:,:,2)=0;
subplot(2,2,4);
imshow(B);


Convert Image into One dimensional

a = imread('cameraman.tif');

[r c]=size(a);

Len=r*c;

b=reshape(a,[1 Len]);


Counting the Number of Objects in an
Image
clc;
clear;
close all;
InputImage=imread('eight.tif');
subplot(2,2,1);
imshow(InputImage);title('InputImage');
BinaryImage=im2bw(InputImage);
subplot(2,2,2);
imshow(BinaryImage);
ComplementImage=imcomplement(BinaryImage);
subplot(2,2,3);
imshow(ComplementImage);
HolesClearedImage = imfill(ComplementImage,'holes');
subplot(2,2,4);
imshow(HolesClearedImage);title('HolesClearedImage');
[L,Num] = bwlabel(HolesClearedImage)
for i=1:3
figure;
imshow(L==i);
pause(2)
end

Advantages and Disadvantages of MATLAB

 Advantages
 Ease of use
 Platform independence
 Predefined functions
 Plotting
 Disadvantages
 Can be slow
 Expensive


Thank You…


Introduction to MATLAB

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