Introduction to MATLAB - PowerPoint

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					Introduction to MATLAB
The language of Technical Computing
MATLAB

 MATrix LABoratory- Everything is
  represented by matrices!
 It is a program for doing Numerical
  Computation.
 Also used widely as a programming
  language to develop tools for Machine
  Learning.
Why MATLAB?
 Large toolbox of numeric/image library
  functions.
 Very useful for displaying, visualizing data.
 High-level: focus on algorithm structure,
  not on low-level details.
 allows quick prototype development of
  algorithms.
 It is an Interpreter, not as fast as
  compiled code.
The MATLAB Environment
Variables
 MATLAB treats all variables as matrices.
  For our purposes a matrix can be thought
  of as an array, in fact, that is how it is
  stored.
 Vectors are special forms of matrices and
  contain only one row OR one column.
 Scalars are matrices with only one row
  AND one column.
MATLAB Programming
 The symbol “%” is used to indicate a
  Comment.
 A “;” at the end of the line implies
  MATLAB won‟t print the output of the
  statement. Otherwise it will print the
  output, which is sometimes useful for
  printing variable values.
MATLAB Programming
a = [1,2,3,4]
MATLAB Output:
a=
   1 2 3 4

a=[1,2,3,4]; %Notice the semicolon
MATLAB Output:
<Empty>
Command Line
 MATLAB's command line is like a
  standard shell:
- Up arrow to recall commands without
  retyping and down arrow to go forward.
 Opening a new file in editor:
>> edit test.m
 MATLAB source file extension is .m.
 Running a program : >> test
MATLAB Programming
 a = [1 2; 3 4]; % Creates a 2x2 matrix
 The simplest way to create a matrix is to
  list its entries in square brackets. The ";"
  symbol separates rows; the (optional) ","
  separates columns.
 N = 5 % A scalar
 v = [1 0 0] % A row vector
MATLAB Programming
 v = [1; 2; 3] % A column vector
 v = v‟
Transpose a Vector or Matrix(row to
  column and column to row)
 v = []
Empty Vector
MATLAB Programming
 m = zeros(2, 3)
Creates a 2x3 matrix of zeros
 v = ones(1, 3)
Creates a 1x3 matrix (row vector) of ones
 m = eye(3) %Identity matrix (3x3)
 v = rand(3, 1)
 Randomly filled
3x1 matrix (column vector)
Indexing in MATLAB
 REMEBER: Indices always start from
  “1”, not “0”.
 Matrix(ROW#,COLUMN#)
 m(1,3) %1st row 3rd column
 m(2,:) %access whole second row
 m(:,3) %access whole second column
Operators
 Assignment = a = b (assign b to a)
 Addition + a + b
 Subtraction - a -b
 Multiplication * or .* a*b or a.*b
 Division / or ./ a/b or a./b
 Power ^ or .^ a^b or a.^b
 A “.” means element wise operation
Conditional Structures

for i=1:2:7 %Loop from 1 to 7, steps of 2
      if(i==3)
             disp(„i is 3‟) %print output
      elseif(i==5)
             disp(„i is 5‟)
      end
end
Functions

 All functions are separate m-files.
 The first line in a function file must be of
  this form:
  function [outarg_1, ..., outarg_m] =
  myfunction(inarg_1, ..., inarg_n)
 The function name should be the same as
  that of the file.
Function Example
   myfunction.m

function y = myfunction(x)

a = [-2 -1 0 1];
y = a + x;
Function Example
   anotherfunction.m

function [y, z] = anotherfunction(a, b)



    y = a + b;
    z = a - b;
Plotting



x=rand(1,100);
y=rand(1,100);
plot(x,y,‟*‟);
Plotting
 To put a label on X-Axis
xlabel(„my x label‟);

 To put a label on Y-Axis
ylabel(„my y label‟);

 To put a Title of the Plot
title(„my title‟);
MATLAB Image Processing
 Image Processing Toolbox is needed.
 I=imread(„cute_baby.jpg‟); %read Image
  imshow(I) %show image
MATLAB Image Processing
I2=rgb2gray(I); % convert RGB to gray
imwrite(I2, „cute.jpg‟); % save gray image
figure, imshow(I2) % image in new figure
MATLAB Image Processing
figure,imhist(I2) % show histogram
MATLAB Image Processing
   From the histogram, we see that the
    image intensity is missing low values, only
    high values are present.
MATLAB Image Processing
I3 = histeq(I2); %Histogram Equalization
figure, imhist(I3);
MATLAB Image Processing
figure, imshow(I2) %Original image
figure, imshow(I3) % Equalized Image
Help with MATLAB
 Type help at the MATLAB prompt or
  help followed by a function name for help
  on a specific function.
 Online documentation for MATLAB at
  the MathWorks website:
 www.mathworks.com
 There are also numerous tutorials online
  that are easily found with a web search.