MATLAB FOR
PATTERN
RECOGNITION
By: Özge Öztimur
How Much Do We Know?

Anybody who has never used
MATLAB?
MATLAB Environment

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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.
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.
Everything is a Matrix
Each variable in MATLAB is a matrix.
 For example:
>> a=1;
>>size(a)
ans=
1 1

Creating Matrices
>> a = [ 1 2 2 1 ]
a=1221
>> b= [1; 2; 2; 1]
b=
1
2
2
1
Accessing a Matrix
>> a=[1 2; 3 4]
a=
12
34
>> a(2,1)
ans=
3
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.

Flow Control-IF
>> if a+b==5
m=1;
elseif a+b==3
m=2;
end
>>
Flow Control-Switch
>> switch (rem(n,4)==0) + (rem(n,2)==0)
case 0
M=0
case 1
M=1
otherwise
M=2
end
Loops
>> a = [ 0.8 0.1; 0.2 0.9 ]
>> x = [ 1; 0 ]
>> for i = 1:20
x = a*x
end

Avoid using Loops in Matlab.
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.

Read & Write Files
Load, Save,Saveas
 Textread
…
 There are many other functions for file
operations. Check File I/O part in
Mathwork’s Help.

Function Definition

Name of the function and the file should be
the same.
function[output1,output2]=example(input)
Example – Generating
Random Numbers

Generate random numbers of size
5x3 (5 rows, 3 columns);
>> a=randn(5,3);
Example-Distributions

Parameter Estimation Examples:

Normal Distribution
>>[mu,sigma]=normfit(data);

Binomial Distribution
>> phat=binofit(data,n)
…
Example-Probability Density
Function
Pdf gives the probability density
function for a specified distribution
>> Y=pdf(name,X,A)
 Where name is the name of the
distribution, X is the data and A is the
parameters for the given distribution.

Example-Maximum
Likelihood Estimation
mle gives the maximum likelihood
estimation
 >> mle(data);
 >> mle(data,’distribution’,dist)
 Where dist is the name of the
distribution

Graphical Representation
Generally ‘plot’ is used for drawing
graphics.
>>plot(x) ;
plots the columns of x versus their
index.
Many options are provided for this
function.

Refer To

http://www.mathworks.com/access/hel
pdesk/help/helpdesk.html

Course Web Page:
www.ceng.metu.edu.tr/courses/secon
dprog/ceng564/