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

27-28 Sept,2012 2MATLAB workshop under CSI

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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


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Toolboxes provided By MATLAB1. Aerospace Simulation2. Neural Network 3. Parallel Computing 4. Image Acquisition 5. Image processing 6. Genetic Algorithm 7. Fuzzy Logic 8. Database processing9. Video and Image processing 10. Control System 11. Signal Processing 12. Statistics 13. Financial Toolbox 14. Curve fitting


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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


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Structure of MATLAB


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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


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Useful Commands

The two commands used most by Matlabusers are

>>help functionname

>>lookfor keyword


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Variables No need for types. i.e.,

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

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

int a;double b;float c;

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


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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


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Variable(cont…)

Initialization using shortcut statements– colon operator “first:increment:last”

>> x = 1:2:10x =1 3 5 7 9

>> y = 0:0.1:0.5y = 0 0.1 0.2 0.3 0.4 0.5


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Variable(cont…)


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Array


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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


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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


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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


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Built-in Math function

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


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Built in Functions

sort sortrows mod(num,2)


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Built in function related to String


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Limit and Integration


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Differentiation


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Solving Equations

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


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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


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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)


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Generating Vectors from functions zeros(M,N) MxN matrix of zeros

ones(M,N) MxN matrix of ones

rand(M,N) MxN matrix of uniformly distributed

random numbers on (0,1)

x = zeros(1,3)x =

0 0 0

x = ones(1,3)x =

1 1 1

x = rand(1,3)x = 0.9501 0.2311 0.6068


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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.


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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.


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


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Matrices Operations

Given A and B:

Addition Subtraction Product Transpose


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Operators (Element by Element)

.* : element-by-element multiplication

./ : element-by-element division

.^ : element-by-element power


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The use of “.” – “Element” Operation

K= x^2Error: ??? Error using ==> mpower Matrix must be square.B=x*yError:??? Error using ==> mtimes Inner matrix dimensions must agree.

A = [1 2 3; 5 1 4; 3 2 1] A = 1 2 3 5 1 4 3 2 -1

y = A(3 ,:)

y= 3 4 -1

b = x .* y

b= 3 8 -3

c = x . / y

c= 0.33 0.5 -3

d = x .^2

d= 1 4 9

x = A(1,:)

x= 1 2 3


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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)


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Displaying Data/Text


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Displaying Data/Text(cont…)


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Import/Export Data from Command


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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


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Flow Control

if for while break continue switch and case


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Control Structures If Statement Syntax

if (Condition_1)MATLAB Commands

elseif (Condition_2) MATLAB Commands

elseif (Condition_3) MATLAB Commands

else MATLAB Commands

end

Some Dummy Examples

if ((a>3) & (b==5)) Some Matlab Commands;end

if (a<3) Some Matlab Commands;elseif (b~=5) Some Matlab Commands;end

if (a<3) Some Matlab Commands;else Some Matlab Commands;end


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Control Structures

For loop syntaxfor i=start: Last index

MATLAB Commandsend

Some Dummy Examples

for i=1:100 Some Matlab Commands;end

for j=1:3:200 Some Matlab Commands;end

for m=13:-0.2:-21 Some Matlab Commands;end

for k=[0.1 0.3 -13 12 7 -9.3] Some Matlab Commands;end


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Control Structures

While Loop Syntax

while (condition)MATLAB Commands

end

Dummy Example

while ((a>3) & (b==5)) Some Matlab Commands;end

% while loop i=1;while(i<10) disp(i); i=i+1;end


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

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


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Switch and case


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Continue statement


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Break statement


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Use of M-File

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

Save file as Denem430.m


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Solution

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

A =

'MATLAB' 'SIMULINK'


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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

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

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


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How to read a text file

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

Ans hello


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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


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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


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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);

Calculate sin(.) of the x-array

Plot the y-array

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

>>y=sin(x);

>>plot(y)


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Plot the function e-x/3sin(x) between 0≤x≤4π Create an x-array of 100 samples between 0

and 4π.

Calculate sin(.) of the x-array

Calculate e-x/3 of the x-array

Multiply the arrays y and y1

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

>>y=sin(x);

>>y1=exp(-x/3);

>>y2=y*y1;27-28 Sept,2012 56

MATLAB workshop under CSI Student Chapter

Plot the function e-x/3sin(x) between 0≤x≤4π Multiply the arrays y and y1 correctly

Plot the y2-array>>y2=y.*y1;

>>plot(y2)

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

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7


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Display Facilities plot(par1,par2)

Example:>>x=linspace(0,4*pi,100);>>y=sin(x);>>plot(y)>>plot(x,y)

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

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7


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Neural Network(NN)


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How to Design Neural Network1. Collect data2. Create the network3. Configure the network4. Initialize the weights and biases5. Train the network6. Validate the network7. Use the network


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Simple Neuron/1st layer Perceptron

bX1 wb=1

w1 y

w2 X2

E


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Transfer Function


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Vectors used in NN


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Neural Network Architecture


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Multilayer NN


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How to open Neural Network Tool>>nftool


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Graph Plot


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Display Facilities

title(.)

xlabel(.)

ylabel(.)

>>title(‘This is the sinus function’)

>>xlabel(‘x (secs)’)

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

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1This is the sinus function

x (secs)

sin(

x)


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GUI(Graphical User Interface)


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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


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DIALOG BOX

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

msgbox('hello');


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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


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GUI…


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PUSH BUTTON


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TOGGLE BUTTON


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RADIO BUTTON


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CHECKBOX


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EDIT TEXT


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STATIC TEXT


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SLIDER


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FRAME


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LISTBOX


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POPUP MENU


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AXES


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ALIGN OBJECTS


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MENU EDITOR


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M FILE EDITOR


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PROPERTY INSPECTOR


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RUN


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PUSH BUTTON


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WRITE THE CODE BELOW THE CALLBACK

a =imread('cameraman.tif');

imshow(a);


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RUN THE PROGRAM OR PRESS F5


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RIGHT CLICK PUSH BUTTON & GO FOR PROPERTY INSPECTOR


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CHOOSE AXES


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RIGHT CLICK AXES & GO FOR PROPERTY INSPECTOR


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CHANGE THE STRING AND TAG VALUE


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axes(handles.one);

imshow(a);


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RUN THE PROGRAM


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CODE


axes(handles.one);

imshow(a);


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TOGGLE BUTTON


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RIGHT CLICK TOGGLE & GO FOR PROPERTY INSPECTOR


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RIGHT CLICK TOGGLE & GO FOR M FILE EDITOR


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a=get(hObject,'Value');

if a ==1 a =imread('cameraman.tif');

axes(handles.one);

imshow(a); else a =imread('greens.jpg');

axes(handles.one);

imshow(a); end


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RUN THE PROGRAM


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RIGHT CLICK CHECK BOX & GO FOR PROPERTY INSPECTOR


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RIGHT CLICK CHECK BOX & GO FOR M FILE EDITOR


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RUN THE PROGRAM


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Image Processing


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How to read an image

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

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


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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)


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How to read an audio file

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


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How to read an video file

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


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Add two images

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

I = imread('rice.tif'); J = imadd(I,Irice50); subplot(1,2,1), imshow(I) subplot(1,2,2), imshow(J)


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Subtract two images

I = imread('rice.tif'); Iq = imsubtract(I,Irice50); subplot(1,2,1), imshow(I)subplot(1,2,2), imshow(Iq)


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Convert image to gray and binaryclc;clear;close alla= 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);


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RGB componenta=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);


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Convert Image into One dimensional

a = imread('cameraman.tif');

[r c]=size(a);

Len=r*c;

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


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Counting the Number of Objects in an Imageclc;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


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Advantages and Disadvantages of MATLAB Advantages

Ease of use Platform independence Predefined functions Plotting

Disadvantages Can be slow Expensive


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Thank You…


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introduction to matlab

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