MATLAB FOR PATTERN RECOGNITION

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MATLAB FOR PATTERN RECOGNITION

• By Özge Öztimur

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How Much Do We Know?

• Anybody who has never used MATLAB?

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MATLAB Environment

• Workspace Variables defined so far.
• Command History
• Command Window
• Edit Window
• Plot Window
• Current Directory Start by setting the current
  directory to the directoy that you are working.
  Generally, it is where your files are.

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LOOKFOR HELP

• LOOKFOR Type lookfor smth to learn the name of
  functions that are related to smth.
• HELP Type help function_name to learn how that
  function works, its inputs and outputs.

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Everything is a Matrix

• Each variable in MATLAB is a matrix.
• For example
• gtgt a1
• gtgtsize(a)
• ans
• 1 1

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Creating Matrices

• gtgt a 1 2 2 1
• a 1 2 2 1
• gtgt b 1 2 2 1
• b
• 1
• 2
• 2
• 1

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Accessing a Matrix

• gtgt a1 2 3 4
• a
• 1 2
• 3 4
• gtgt a(2,1)
• ans
• 3

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Matrix Operations

• Matrix operations like,
• Matrix addition, subtraction, multiplication
• Determinant of a matrix
• Inverse of a matrix
• Transpose of a matrix
• Element by element multiplication, division
• are defined in MATLAB.

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Flow Control-IF

• gtgt if ab5
• m1
• elseif ab3
• m2
• end
• gtgt

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Flow Control-Switch

• gtgt switch (rem(n,4)0) (rem(n,2)0)
• case 0
• M0
• case 1
• M1
• otherwise
• M2
• end

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Loops

• gtgt a 0.8 0.1 0.2 0.9
• gtgt x 1 0
• gtgt for i 120
• x ax
• end
• Avoid using Loops in Matlab.

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M-Files Scripts And Functions

• Scripts Do not accept input arguments or return
  output arguments.They operate on data in the
  workspace.
• M-Files can accept input arguments and return
  output arguments.Internal variables are local to
  the function.

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Read Write Files

• Load, Save,Saveas
• Textread
• There are many other functions for file
  operations. Check File I/O part in Mathworks
  Help.

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Function Definition

• Name of the function and the file should be the
  same.
• functionoutput1,output2example(input)

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Example Generating Random Numbers

• Generate random numbers of size 5x3 (5 rows, 3
  columns)
• gtgt arandn(5,3)

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Example-Distributions

• Parameter Estimation Examples
• Normal Distribution
• gtgtmu,sigmanormfit(data)
• Binomial Distribution
• gtgt phatbinofit(data,n)

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Example-Probability Density Function

• Pdf gives the probability density function for a
  specified distribution
• gtgt Ypdf(name,X,A)
• Where name is the name of the distribution, X is
  the data and A is the parameters for the given
  distribution.

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Example-Maximum Likelihood Estimation

• mle gives the maximum likelihood estimation
• gtgt mle(data)
• gtgt mle(data,distribution,dist)
• Where dist is the name of the distribution

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Graphical Representation

• Generally plot is used for drawing graphics.
• gtgtplot(x)
• plots the columns of x versus their index.
• Many options are provided for this
• function.

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Refer To

• http//www.mathworks.com/access/helpdesk/help/help
  desk.html
• Course Web Page
• www.ceng.metu.edu.tr/courses/secondprog/ceng564/