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1

• Data mining
• Demo 1

• 28.11.2007

2
Introduction

• This slide set contains
• Very easy and supervised introductory material
  for MATLAB
• Homework (Task 1 and Task 2 in the last two
  slides)
• If you are already expert in MATLAB then you can
  skip the introduction and start to work with the
  homeworks
• By returning homeworks (a short report about the
  accomplished tasks) one can get credits for the
  final exam (total 3 x 2points, exam max is 4x6
  24 points)
• The reports for the tasks of Demo 1 must be
  returned not later than 10.12.2007
• The reports can be returned by e-mail
  (sami.ayramo_at_jyu.fi), or to the office room (Ag
  C416.2), or to mailbox (which can be found two
  meter away from the office door)
• Some additional codes that may be useful for the
  homework can be found at http//users.jyu.fi/sami
  ayr/DM/demot

3
Requirements

• Basic computer skills (e.g., starting
  applications, opening, closing and saving files,
  cutting and pasting text, directory structures,
  )
• Know how to use a text editor, such as Windows
  Notepad, that you can use to write MATLAB
  programs (MATLAB also has its own built-in text
  editor which you can use)
• Basic algebra and trigonometry
• Knowledge of basic linear algebra (i.e., concepts
  such as matrix, vector, inverse etc.) would also
  be very helpful
• While you are following this introduction, have
  MATLAB running in a separate window and perform
  and experiment with the examples
• This introduction is extracted, modified and
  compressed from the one available at the
  Mathworks Student Center
• http//www.mathworks.com/academia/student_center/t
  utorials/

4
Facts about MATLAB

• MATLAB is a computer program
• for solving the sorts of mathematical problems
  frequently encountered, for example, data mining,
  data analysis, statistics, simulation,
  engineering, mathematical modelling
• Built-in features of MATLAB to enables effortless
  solving of a wide variety of numerical problems
• from the very basic, such as a system of 2
  equations with 2 unknowns
• X 2Y 24
• 12X - 5Y 10
• to the more complex, such as factoring
  polynomials, fitting curves to data points,
  making calculations using matrices, performing
  signal processing operations such as Fourier
  transforms, and building and training neural
  networks.
• MATLAB can be used to plot many different kinds
  of graphs, enabling the visualization of complex
  mathematical functions and laboratory data
• The three images below have been created using
  MATLAB plotting functions

Images are taken from www.mathworks.com
5
Starting MATLAB

• You can start MATLAB by double-clicking on the
  MATLAB icon
• The MATLAB Desktop will then pop-up

6
Entering commands in MATLAB

• gtgt is the command prompt,
• Type a command at a command prompt and MATLAB
  executes the command you typed in, and then
  prints out the result
• Ex1 Enter a simple MATLAB command date to see
  how it works
• Ex2 Try also the clc command (clear command
  window)
• Ex3 To exit MATLAB can just enter quit at the
  MATLAB command prompt
• To get a good feel for the kinds of things you
  can use MATLAB for, also many different demos are
  provided, all accessible from a demo window that
  is popped up when you type, demo, at the command
  prompt

7
Getting help

• MATLAB has an extensive help system built into
  it, containing detailed documentation and help
  information on all of the commands and functions
  of MATLAB
• To obtain help on a given function there are
  three main functions help, helpwin (short for
  help window) or doc (short for documentation).
• help and helpwin give you the same information,
  but in a different window, the doc command
  returns an HTML page with a lot more information
• Ex4 Find help on the date function using the
  different functions
• Another source of help is the MATLAB help browser
  
• you can invoke the MATLAB help browser by
• typing helpbrowser at the MATLAB command prompt
• clicking on the help button ?
• by selecting Start-gtMATLAB-gtHelp from the MATLAB
  desktop
• Tutorials and documents can also be found at
  www.mathworks.com in large amounts

8
Working with variables

• Variables are a fundamental concept in MATLAB and
  are used all the time
• In its simplest mode of use, MATLAB can be used
  just like a pocket calculator
• MATLAB supports all the basic arithmetic
  operations , -, , /, , etc. and you can
  group and order operations by enclosing them in
  parentheses
• Ex5 Try the following calculator-like operations
  with MATLAB by typing
• 4 10
• 5 10 6
• (6 6) / 3
• 92
• What is ans? In short ans is short for "answer",
  and is used in MATLAB as the default variable
  name when none is specified
• Ex6 Check the value of ans by typing ans
• Ex7 Try to change the value of ans by typing ans
  6
• You can also define and use your own variables
• Ex8 Create three variables, chech the value of
  the first one, and calculate the average. For
  instance, enter the following commands
• a 10
• b 20
• c 30
• a
• the_average (a b c) / 3

9
Working with variables

• If you have defined a lot of different variables,
  you probably can't remember all the variable
  names you have defined. Therefore, it is nice to
  get a list of all the variables currently
  defined. Simply typing whos at the command prompt
  will return to you the names of all variables
  that are currently defined.
• Ex9 Try the sequence of the following commands
• clear
• a 5
• b 6
• whos
• Typing clear at the command prompt will remove
  all variables and values that were stored up to
  that point.
• Ex10 For example, continue from the above
  example
• whos
• clear
• whos

10
Working with variables

• If a command is followed by a semicolon () then
  MATLAB evaluates the expression and store the
  result internally, but will not print put the
  result
• The user is mainly concerned only with some final
  result in your MATLAB sessions, which will be
  calculated by combining many temporary,
  intermediate variables and by appending a
  semicolon to the expressions that assign values
  to the temporary, intermediate variables causes
  their results to not be printed
• Ex11 Compare the following expressions
• a 4 5
• b 5 6

11
Working with variables

• In MATLAB, there are some specific rules for what
  you can name your variables
• Only use primary alphabetic characters (i.e.,
  "A-Z"), numbers, and the underscore character
  (i.e., "_") in your variable names.
• You cannot have any spaces in your variable
  names
• For example, using "this is a variable" as a
  variable name is not allowed, but
  "this_is_a_variable" is fine
• MATLAB is case sensitive.
• For example, "A_VaRIAbLe", "a_variable",
  "A_VARIABLE", and "A_variablE" would all be
  considered distinct variables in MATLAB
• Using single quotes one can also assign pieces of
  text to variables
• Ex12 For example, try
• some_text 'This is some text assigned to a
  variable!'
• some_text
• Be careful not to mix up variables that have text
  values with variables that have numeric values in
  equations

12
MATLAB the matrix laboratory

• Three fundamental concepts in MATLAB, and in
  linear algebra, are
• A scalar is simply just a fancy word for a
  number (a single value)
• A vector is an ordered list of numbers
  (one-dimensional)
• In MATLAB they can be represented as a row-vector
  or a column-vector
• A matrix is a rectangular array of numbers
  (multi-dimensional)
• In MATLAB, a two-dimensional matrix is defined by
  its number of rows and columns
• Both scalars and vectors can be considered a
  special type of matrix.
• A scalar is a matrix with a row and column
  dimension of one (1-by-1 matrix)
• A vector is a one-dimensional matrix one row
  and n-number of columns or n-number of rows and
  one column
• All calculations in MATLAB are done with
  "matrices". Hence the name MATrix LABoratory.

13
MATLAB the matrix laboratory

• In MATLAB matricies are defined inside a pair of
  square braces ()
• A comma (,) and semicolon () are used as a row
  separator and column separator, respectfully
• Note you can also use a space as a row
  separator, and a carriage return (the enter key)
  as a column separator as well
• Ex13 Try the examples to see how a scalar, and
  row and column vectors, can be created
• my_scalar 3.1415
• my_vector1 1, 5, 7
• my_vector2 1 5 7

14
MATLAB the matrix laboratory

• What about a two dimensional matrix?
• Ex14 Create a 4-by-3 matrix called my_matrix
  with the numbers 8, 12, and 19 in the first row,
  7, 3, 2 in the second row, 12, 4, 23 in the third
  row, and 8, 1, 1, in the fourth row by typing the
  following command
• my_matrix 8, 12, 19 7, 3, 2 12, 4, 23 8,
  1, 1
• You can also combine different vectors and
  matrices together to define a new matrix
• Remember that the output needs to be a valid
  rectangular matrix
• Ex15 Construct a matrix from row vectors by
  typing the following lines
• row_vector1 1 2 3
• row_vector2 3 2 1
• matrix_from_row_vec row_vector1
  row_vector2
• Ex16 Construct a matrix from column vectors by
  typing the following lines
• column_vector1 13
• column_vector2 28
• matrix_from_col_vec column_vector1
  column_vector2
• Ex17 Construct a matrix from a 4x3 matrix by
  typing the following lines
• my_matrix 8, 12, 19 7, 3, 2 12, 4, 23 8,
  1, 1
• combined_matrix my_matrix, my_matrix

15
Indexing vectors and matrices

• Once a vector or a matrix is created you might
  needed to extract only a subset of the data, and
  this is done through indexing.
• In a row vector the left most element has the
  index of one.
• In a column vector the top most element has the
  index of one.
• Ex17 Create vectors my_vector1 and
  my_vector2 and try to index into its values
• my_vector1 1 5 7
• my_vector2 1 5 7
• my_vector1(1)
• my_vector2(2)
• my_vector1(3)
• my_vector2(1)
• my_vector2(2)
• my_vector2(3)
• The process is much the same for a
  two-dimensional matrix. The only difference is
  that you have to specify both the row and column
  indices.
• Ex18 Access the value of 4 in my_matrix
• my_matrix 8, 12, 19 7, 3, 2 12, 4, 23 8,
  1, 1
• my_matrix(3,2)
• Note The row number is first, followed by the
  column number.

16
Indexing vectors and matrices

• You can also extract any contiguous subset of a
  matrix, by referring to the row range and column
  range you want.
• Ex19 Try the following examples
• mat 1 3 2 3 5 6 5 7 4 8 1 2 3 4 3 2 8 4 7 3
  2 3 2 3 4 1 4 2
• mat(24,47)
• mat(12,13 56)
• You can change a number in a matrix by assigning
  to it
• Ex20 Try to change the value of an element by
  the following commands
• mat 1 3 2 2 3 4 7 3 2 1 4 2
• mat(2,2) 999

17
Element-by-element operations

• Element-by-element operations are performed on
  two vectors or matrices of the same size to get
  the result of the same size
• For example, "element-by-element multiplication"
  of two vectors 1 2 3 and 4 5 6 would give you
  4 10 18.
• The element-by-element operators in MATLAB are as
  follows
• element-by-element multiplication "."
• element-by-element division "./"
• element-by-element addition ""
• element-by-element subtraction "-"
• element-by-element exponentiation "."
• Ex21 Try the following operations (which of
  these works?)
• a1 2 3
• b4 5 6
• c6 7 8
• d6 7 8
• a.b
• a.c
• c.d
• c.d

18
Element-by-element operations

• An additional note about element-by-element
  operators is that you can use them with scalars
  and vectors together
• Ex22 Try the following operation
• a 1 2 3 4 5 6
• b a . 2
• You can similarly use ".", "", and "-" with a
  vector and scalar.
• Ex23 Try some examples
• c a . 2
• d a 2
• e a 2
• The reason that element-by-element multiplication
  and exponentiation operators have "." appended to
  the front of them, while the element-by-element
  addition and subtraction operators do not, is
  that there are other kinds of multiplication,
  division, and exponentiation operators (denoted
  by "" , "/"and ") for matrices, which are not
  element-by-element

19
Matrix operations

• Element-by-element operations allow us to compute
  things on an element-by-element basis, but matrix
  operations allow us to perform matrix-based
  computation.
• For example, the multiplication of two matrices,
  represented by "", performs a dot product of the
  two matrices. What the dot product does is that
  it first multiplies the corresponding elements
  (i.e., same position elements) of the two
  vectors, similar to what element-by-element
  multiplication does, and then adds up all the
  results of these multiplications to get a single,
  final number as the answer.
• Ex24 Try the following matrix multipilication
• a 1 2 3
• b 4 5 6
• a b
• To get the answer "32", what MATLAB first
  performs the multiplications of the corresponding
  elements of the two vectors "14 4", "2510",
  and "3618". Then, to get the final answer of
  "32", MATLAB adds all these multiplications
  together "4101832".
• The length of vectors and the size of matrices
  can be found by length and size functions
• Ex25 Try the following examples
• a 1 2 3
• length(a)
• mat 1 3 2 2 3 4 7 3 2 1 4 2
• size(mat)

20
Plotting

• The most basic plotting command in MATLAB is the
  plot command. The plot command, when called with
  two same-sized vectors X and Y, makes a
  two-dimensional line plot for each point in X and
  its corresponding point in Y. In other words, it
  will draw points at (X(1),Y(1)), (X(2),Y(2)),
  (X(3),Y(3)), etc., and then connect all these
  points together with lines.
• Ex26 Try a very simple example to illustrate
  what the plot command does
• simple_x_points 1 2 3 4 5
• simple_y_points 25 0 20 5 15
• plot(simple_x_points, simple_y_points)
• The ordering of the vectors in the plot command
  is important
• Ex27 Try the reversed order for the previous
  simple example
• plot(simple_y_points, simple_x_points)

21
Plotting

• To add text to a plot, you need to keep the
  figure window open (i.e., type the commands in
  the MATLAB command window while the figure window
  is still open).
• The xlabel/ylabel command prints out a text
  string describing the x-axis/y-axis The title
  command prints out a title for your plot. Typing
  "grid on" at the command prompt, the grid lines
  will be added to the open figure window (typing
  "grid off" will get rid of the grid lines).
• Ex28 Try to use these commands on the previous
  plot
• simple_x_points 1 2 3 4 5
• simple_y_points 25 0 20 5 15
• plot(simple_x_points, simple_y_points)
• xlabel('this is text describing the x-axis')
• ylabel('this is text describing the y-axis')
• title('this is text giving a title for the
  graph')
• grid on

22
Plotting a parabola

• Ex29 Let's look at a more practical example of
  plotting. First you need to create a vector of
  regularly spaced points and a vector of function
  values at those points for some function. Do this
  for the function "y x2" (i.e., a parabola) for
  x values between -5 and 5 and with regular
  spacing of .1
• x_points -5 .1 5
• y_points x_points . 2
• Then plot the x_points against the y_points,
  and get the familiar plot of a parabola
• plot(x_points,y_points)
• xlabel('x-axis') ylabel('y-axis') title('A
  Parabola')
• grid on
• Note The result is very smooth you can't really
  see any of the individual line segments like you
  could for the simple example previously. That is
  because the points are so close together (at
  regular spacings of .1) --- MATLAB is still
  drawing line segments between the points, but
  your eye just can't see them because they are so
  small, and so the result seems to be a smooth
  curve.

23
Multiple plots

• Using the hold command, you can add multiple
  plots in the same figure window, to compare the
  plots for example. (Normally, when you type a
  plot command, any previous figure window is
  simply erased, and replaced by the results of the
  new plot.)
• If you type "hold on" at the command prompt, all
  line plots created after that will be
  superimposed in the same figure window and axes.
  Like wise the command "hold off" will stop this
  behavior, and revert to the default (i.e., new
  plot will replace the previous plot).
• Ex30 Try the following example of how to plot
  several different exponential functions in the
  same axes (you need to define the points on
  x-axis only once)
• x_points -10 .05 10
• plot(x_points, exp(x_points))
• grid on
• hold on
• plot(x_points, exp(.95 . x_points))
• plot(x_points, exp(.85 . x_points))
• plot(x_points, exp(.75 . x_points))
• xlabel('x-axis') ylabel('y-axis')
• title('Comparing Exponential Functions')

24
Subplots

• In order to have multiple plots in the same
  window, but each in a separate part of the window
  (i.e., each with their own axes), you use the
  subplot command. If you type subplot(M,N,P) at
  the command prompt, MATLAB will divide the plot
  window into a bunch of rectangles --- there will
  be M rows and N columns of rectangles --- and
  MATLAB will place the result of the next "plot"
  command in the Pth rectangle (where the first
  rectangle is in the upper left).
• Ex31 Try this example of a line plot, a
  parabola, an exponential, and the absolute value
  function into four rectangles in the same figure
  window
• x_points -10 .05 10
• line 5 . x_points
• parabola x_points . 2
• exponential exp(x_points)
• absolute_value abs(x_points)
• subplot(2,2,1)plot(x_points,line)
• title('Here is the line')
• subplot(2,2,2)plot(x_points,parabola)
• title('Here is the parabola')
• subplot(2,2,3)plot(x_points,exponential)
• title('Here is the exponential')
• subplot(2,2,4)plot(x_points,absolute_value)
• title('Here is the absolute value')

25
Line Plots in Three Dimensions

• MATLAB cover two different kinds of
  three-dimensional plots you can do in MATLAB, 1)
  three-dimensional line plots and 2) surface mesh
  plots.
• The three-dimensional line plots are analagous to
  the two-dimensional line plots created with the
  plot command. The only difference is that the
  command has a "3" added to it, plot3, and that it
  requires an extra input, Z, for the third
  dimension.
• Ex32 A simple example of using the plot3
  command, and the resulting output figure window
  (notice that you can also here use hold and
  subplot in the same way too)
• X 10 20 30 40
• Y 10 20 30 40
• Z 0 210 70 500
• plot3(X,Y,Z) grid on
• xlabel('x-axis') ylabel('y-axis')
  zlabel('z-axis')
• title('Pretty simple')

26
Three-Dimensional Surface Mesh Plots

• The mesh and meshgrid commands can be used to
  create surface mesh plots, which show the surface
  of three-dimensional functions, such as "z x2
  y2"
• The way it works is that
• Generate a grid of points in the xy-plane using
  the meshgrid command
• Evaluate the three-dimensional function at these
  points
• Create the surface plot with the mesh command
• Ex33 Try to generate the meshgrid and generate
  the surface mesh plot
• x_points -10 1 10
• y_points -10 4 10
• X, Y meshgrid(x_points,y_points)
• Z X.2 Y.2
• mesh(X,Y,Z)
• xlabel('x-axis')
• ylabel('y-axis')
• zlabel('z-axis')

27
MATLAB scripts

• A MATLAB script is an ASCII text file that
  contains a sequence of MATLAB commands
• the commands contained in a script file can be
  run, in order, in the MATLAB command window
  simply by typing the name of the file at the
  command prompt
• Any text editor, such as Microsoft Windows
  Notepad, or wordprocessor, such as Microsoft
  Word, can used to create scripts, but the scripts
  must always be saved as simple text documents
  (i.e., in the "Save As" dialogue box, choose
  "Text Document" or its equivalent for "Save as
  type").
• It is easiest to create scripts using MATLAB's
  built-in text editor, which automatically just
  saves files as ASCII text files for you.
• When naming script files, you need to append the
  suffix ".m" to the filename, for example
  "my_script.m".
• Scripts in MATLAB are also called "M-files"
  because of this, and the ".m" suffix tells MATLAB
  that the file is associated with MATLAB.

28
Creating MATLAB script

• Ex34 Create a simple script that calculates the
  average of five numbers that are stored in
  variables. Start with typing edit
  average_script.m after the command prompt. Then
  add the following contents of the script file
  "average_script.m" in the MATLAB's built-in text
  editor
• a simple MATLAB m-file to calculate the average
  of 5 numbers.
• first define variables for the 5 numbers
• a 5
• b 10
• c 15
• d 20
• e 25
• now calculate the average of these and print it
  out
• five_number_average (a b c d e) / 5
• five_number_average
• NOTE! Save the above script for the later use!
• The text in green (i.e., the lines starting with
  --- all comment lines must start with ) are
  comments.

29
Running MATLAB script

• If you saved the above script "average_script.m"
  into the present working directory, then it can
  be run simply by typing average_script at the
  MATLAB command prompt.
• Ex35 Try to run it using the following sequence
  of commands in the command prompt
• clear
• whos
• pwd
• dir
• average_script
• whos

30
Saving variables 1

• The save command can be used to save all or only
  some of your variables into a MATLAB data file
  type called MAT-file
• If you want to choose the name of the file
  yourself, you can type save followed by the
  filename you want to use.
• MATLAB will then save all currently defined
  variables in a file named with the name you chose
  followed by the suffix ".mat" (for example, if
  you chose the name my_variables MATLAB would save
  as "my_variables.mat" in your present working
  directory).
• Before saving you should change your present
  working directory to one of your own directories
  (such as some directory on your floppy diskette),
  or specify the complete path to where you want
  MATLAB to save your variables (for example
  "a\my_variables\my_vars").
• Ex36 Try this example of using save
• clear
• who
• cd c\my_variables (replace this with your own
  folder)
• pwd present working directory
• a 10
• b 20
• c 30
• d sqrt((a b c)/pi)
• who
• save my_chosen_filename (replace this with your
  own filename)
• dir
• clear
• who

31
Saving variables 2

• The above use of the save command saved all the
  MATLAB workspace defined variables. If you just
  want to save some of your variables, you simply
  list the variables you want to save after typing,
  save and the filename.
• Ex37 Try to save only the variables a and c
• clear
• who
• a 10
• b 20
• c 30
• who
• pwd
• save some_of_my_variables a c (replace this with
  your own filename)
• dir
• clear
• who

32
Loading variables 1

• The load command is used for loading variables
  back in later to use them again. Typing load
  followed by a filename (without the ".mat"
  suffix) will search the MATLAB path (refer to the
  next lesson regarding the MATLAB path) for the
  file, "filename.mat", and load all the variables
  saved in that file (for example, typing load
  my_vars would cause MATLAB to search for
  "my_vars.mat" and load the variables saved in
  it).
• Ex38 Try this example of loading variables back
  into MATLAB
• clear
• who
• cd c\my_variables (replace this with your own
  folder)
• dir
• load my_chosen_filename (replace this with your
  own filename)
• who
• a
• clear
• who
• load some_of_my_variables (replace this with
  your own filename)
• who
• c

33
Loading variables 2

• You can also choose to load in only some of the
  variables that are saved in a MATLAB data file
  (MAT-file). To load only some of the variables
  saved in a file back into MATLAB, just type the
  names of the variables you want loaded back in
  after typing load and the filename (without
  ".mat") at the command prompt.
• Ex39 Assuming that variables "a", "ans", "b",
  "c", and "d" are all saved in a file, you can use
  the load command to load only "a" and "c" back
  in
• who
• dir
• whos -file my_chosen_filename (replace this with
  your own filename)
• load my_chosen_filename a c (replace this with
  your own filename)
• who
• a

34
Working with Files, Directories and Paths

• In general, files are managed, organized, and
  accessed in MATLAB in the same way as in
  Microsoft Windows, that is, in a hierarchical
  file system.
• How MATLAB Finds Files?
• MATLAB always look inside your present working
  directory (type pwd at the MATLAB command prompt
  to see your present working directory)
• If the file is not located in the present
  working directory MATLAB will also search in
  other directories that are stored in the MATLAB
  path (The present working directory can also be
  thought of as part of the MATLAB path)
• Ex40 To print out the current MATLAB path type,
  matlabpath or path, at the command prompt
• If you want to store your MATLAB files in some
  directory that does not exist in the matlabpath,
  add the complete path to your directory to the
  MATLAB path.
• Ex41 There are two ways you can append your own
  paths to the MATLAB path
• use the addpath command - type addpath followed
  by the complete path to your directory
• use the path tool of MATLAB - type pathtool at
  the command prompt, or select File-gtSet Path
• addpath a\my_stuff\letters
• matlabpath

35
Useful functions

• pwd - present working directory
• dir, or ls - List directory
• what - List MATLAB-specific files in directory
• cd - Change current working directory
• path, or matlabpath - List the MATLAB search path
• addpath - Add directory to search path
• pathtool - Invoke the path tool interface
• help general - List of general MATLAB commands

36
Exercises

1. Download the well-known Iris data to your working
   directory from http//www.ics.uci.edu/mlearn/MLSu
   mmary.html
2. Import the data into MATLAB by choosing from
   menu File-gtImport data-gt
3. Perform some explorative DM for the Iris data
   set.
4. Make a global summarization for the Iris data
   (for example, compute the mean, median, variance
   and range of the variables)
5. Explore data by plotting 2-dimensional scatter
   plots for each pair of variables (e.g.,
   plotmatrix)
6. Find the two most correlating variables in the
   data (corrcoef)
7. Plot histogram (using, for example, 10 bins) for
   each variable (hist)
8. Compute attribute means and medians for each
   class
9. Compute the variance of all the variables (var)
10. Compute the covariance matrix of the whole data
    (cov)
11. Construct histograms of 10 bins for each Iris
    variable
12. Make 2-dimensional scatter plots for each pair of
    variables on Iris data. Use different markers
    with different colors for different classes

Use help commands and documentation at
http//www.mathworks.com/access/helpdesk/help/tech
doc/matlab.html!!!
37
Task 1

• Load the Iris data set from UCI repository
  http//www.ics.uci.edu/mlearn/MLSummary.html
• A short description of the data is found from the
  lecture slides, Tan et al. Chapter 3 Exploring
  data, slide number 4.
• Expect that you do not know the class names, the
  number of classes etc. of the Iris data set. What
  you know is that you have some data about flowers
  and the attribute names. Then, without prior
  assumptions and knowledge, analyse the data set
  using the available (or self-implemented)
  explorative and summarizing MATLAB tools.
  Document and explain all you can learn from the
  data by exploring. The documentation should
  contain figures and interpretation of useful and
  interesting visual views (different plots,
  colors, histograms,... see the techniques in the
  lecture slides Tan et al. Chapter 3 Exploring
  data). For example
• Can you determine the number of classes by
  exploring (assumed to be unknown)? How?
• Behavior of attributes (correlations, scatters
  (variance/MAD/covariance), ranges, ). What kind
  of preprocessing might be needed? Are there
  redundant attributes? Outliers? And so on..
• other findings?
• Explain what you can learn about data (that
  represents the three flower types). Describe
  carefully your findings and compare your results
  with respect to the known class labels of the
  flowers. Did you find the classes from the data?

38
Task 2

1. Load the synthetic cluster data set from the file
   clusterdata1.data. The data set contains a set of
   generated 7-dimensional clusters. Try to find the
   best possible prototypes for the clusters using
   the MATLAB implementation of the dckmeans.m.
   Before this, exploring and preprocessing the data
   set (see Task 1), try to find all possible
   information for the clustering step (for example,
   data may contain errors, noise, redundancies,
   moreover, you must determine the number of
   clusters and so on). You may also modify the
   dckmeans code (e.g., replace the sample mean
   estimate wih a more robust one such as median).
   Remember that K-means is a local seach method
   (results depend on the initial prototypes, you
   may find the good ones). You can also utilize the
   PCA code in exploration and/or clustering.
2. Document and explain all the steps and all the
   significant facts you can learn from the data by
   exploring, summarization, visualization,
   clustering etc. The documentation should contain
   plots, histograms, etc. with interpretations. If
   you do some prepocessing, transformations,
   scaling for data, report and explain them
   carefully. The most important thing is to
   document the final clustering results (prototypes
   and clusterlabels) that is your refinement for
   the data set.
3. Remember not to only report the findings, but
   also how did you proceed (your mining process)!

Exploit frequently the help commands and
documentation at http//www.mathworks.com/access/h
elpdesk/help/techdoc/matlab.html!!!