An overview of genetic algorithms and their use in Data Mining.

1. GENETIC
ALGORITHMS
AND THEIR APPLICATIONS IN DATA MINING
UNIVERSITY SCHOOL OF INFORMATION AND COMMUNICATION TECHNOLOGY

2. GENETIC ALGORITHMS
• DARWINIAN SELECTION:
Survival of the fittest
Understanding a GA means understanding the simple, iterative processes that
underpin evolutionary change
EXAMPLE: finding largest divisor of a big number
By applying Darwinian selection, only the best solutions will remain, thus
narrowing the search space.

3. BIOLOGICAL BACKGROUND (BASIC CONCEPTS)
• CHROMOSOME:
A set of genes. Chromosome contains the solution in form of genes.
• GENE:
A part of chromosome. A gene contains a part of solution. It determines the
solution. E.g. 16743 is a chromosome and 1, 6, 7, 4 and 3 are its genes.

4. BIOLOGICAL BACKGROUND (BASIC
CONCEPTS) CONTD..
• POPULATION:
• No. of individuals present with same length of chromosome.
• FITNESS:
• Fitness is the value assigned to an individual. It is based on how far or
close a individual is from the solution. Greater the fitness value better the
solution it contains.

5. BIOLOGICAL BACKGROUND (BASIC
CONCEPTS) CONTD..
• FITNESS FUNCTION:
Fitness function is a function which assigns fitness value to the individual. It
is problem specific.

6. FLOWCHART OF A GENETIC ALGORITHM

7. SELECTION
• Selection is the stage of a genetic algorithm in which individual
genomes are chosen from a population for later breeding
(recombination or crossover).
• We will discuss two techniques:
• Roulette Wheel Selection
• Rank Selection

8. ROULETTE WHEEL SELECTION
• Parents are selected according to their fitness.
• The better the chromosomes are, the more
chances to be selected they have.
• Imagine a roulette wheel where are placed all
chromosomes in the population, every has its
place big accordingly to its fitness function.

9. RANK SELECTION
• Rank selection first ranks the population
and then every chromosome receives
fitness from this ranking.
• The worst will have fitness 1, second
worst 2 etc. and the best will have
fitness N(number of chromosomes in
population).

10. OPERATORS
CROSSOVER
• Combine bits and pieces of good parents
• Speculate on new, possibly better children
• By itself, a random shuffle

11. BASIC CONCEPTS CONTD..
MUTATION
• Mutation is random alteration of a string
• Change a gene, small movement in the neighbourhood
• By itself, a random walk

12. DATA MINING
The goal of the data mining process is to extract information from
a data set and transform it into an understandable structure for
further use.

13. EXAMPLE
OCCUPATION: POLITICATION
BELONGS TO :ABC PARTY
AIM:
WANTS TO CONTEST UPCOMING ELECTIONS IN BYTELAND.
PROBLEM:
BUT NOT SURE FROM WHERE HE SHOULD CONTEST HIS
ELECTIONS..
KNOWS DATA MINING …
COLLECTS DATA OF ALL PREVOUS STATE AND
GENERAL ELECTIONS

14. PREPARES THE DATA MAKES IT CONSISTENT AND
NOISELESS
SPLITS INTO TWO EQUAL BUT MUTUALLY EXCLUSIVE
ELEMENTS, A TEST AND A TRAINING DATASET.
SETS PREDICTOR VARIABLE AS LITERACY
RATE, LOCALITY, ETC.
AND THE TARGET WOULD BE: WHETHER A PERSON
X WILL VOTE FOR A PARTY ABC OR NOT.

15. Feeds the input and output variable of training data into
software that run Genetic Algorithms on it
Software process the input of training data set and
matches against its output
E.g. After applying Genetic operators software establishes
two rules
Rule1:if voter X is belongs to locality A then he will vote for
party ABC.
Rule 2:if voter X is literate and belongs to locality A then
he will vote form party ABC.
Feeds the input variable of the test data, applies the rules
obtained from GA and check if the expected output
matches the actual output. Keeps the rule which gets
validated.

16. Now after applying Data mining and using Genetic Algorithms
politician knows that maximum probability of him wining
elections is to contest election from a constituency which have
• Maximum Number of literacy rate
• And falls in locality A.

17. ADVANTAGES
• Concepts are easy to understand due to techniques similar to the
natural processes like inheritance, mutation, etc.
• Can be used where traditional search methods fail.
• Useful where search space is large, complex or poorly understood.

18. ADVANTAGES CONTD..
• Provides us with several local optimums as well as the global
optimum.
• Solves problems with multiple solutions.
• Genetic algorithms are easily transferred to existing simulations
and problems.

19. LIMITATIONS
• Due to poorly known fitness functions, some optimization
problems cannot be solved by Genetic algorithms. These are called
Variant problems.
• There is no assurance of finding a global optimum. It happens very
often when the populations have a lot of individuals.
• Like other artificial intelligence techniques, the genetic algorithm
cannot assure constant optimization response times.

20. LIMITATIONS CONTD..
• While using genetic algorithms, it is true that the entire population
is improving, but this could not be said for an individual within this
population.
• Writing of fitness function must be accurate.

21. APPLICATIONS
• Optimization: GAs have been used in a wide variety of optimization tasks.
• Automatic Programming: for building computational structures like cellular
automata and sorting networks.
• Machine and Robot Learning: used for classification and prediction, and
protein structure prediction.
• Economic models: for development of bidding strategies in the emerging
markets.

22. CONCLUSIONS
• Genetic Algorithms are easy to apply to a wide range of
problems, like TSP, concept learning, etc.
• Results can be very good on some problems while rather poor
on others.
• If we use mutation only, it makes the algorithm very
slow, crossover makes it significantly faster.

23. CONCLUSIONS CONTD..
• They have applications in commercial, educational and scientific
areas.
• Very useful where developer does not have precise domain
expertise, because of their ability to explore and learn from their
domain.

24. THANK YOU