Feed Forward Neural Network Algorithm for Frequent Patterns Mining

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					                                                            (IJCSIS) International Journal of Computer Science and Information Security,
                                                                                                            Vol. 8, No.8, November 2010

           Feed Forward Neural Network Algorithm for
                    Frequent Patterns Mining
                                                          Amit Bhagat1
                                              Department of Computer Applications

                                                       Dr. Sanjay Sharma2
                                          Associate Prof. Deptt. of Computer Applications

                                                       Dr. K.R.Pardasani3
                                                 Professor Deptt. of Mathematics

                             Maulana Azad National Institute of Technology, Bhopal (M.P.)462051, India
                      am.bhagat@gmail.com, 2ssharma66@rediffmail.com,3 kamalrajp@rediffmail.com

Abstract: Association rule mining is used  to find relationships         database many times, so the computational cost is high. In
among items in large data sets. Frequent patterns mining is an           order to overcome the disadvantages of Apriori algorithm and
important aspect in association rule mining. In this paper, an           efficiently mine association rules without generating candidate
efficient algorithm named Apriori-Feed Forward(AFF) based on             itemsets, many authors developed some improved algorithms
Apriori algorithm and the Feed Forward Neural Network is                 and obtained some promising results [9,10, 11, 12, 13].
presented to mine frequent patterns. Apriori algorithm scans
database many times to generate frequent itemsets whereas
                                                                         Recently, there are some growing interests in developing
Apriori-Feed Forward(AFF) algorithm scans database Only                  techniques for mining association patterns without a support
Once. Computational results show the Apriori-Feed                        constraint or with variable supports [14, 15, 16].Association
Forward(AFF) algorithm performs much faster than Apriori                 rule mining among rare items is also discussed in [17,18]. So
algorithm.                                                               far, there are very few papers that discuss how to combine
                                                                         Apriori algorithm and Neural Network to mine association
    Keywords: Association rule mining, dataset scan, frequent
                                                                         rules. In this paper, an efficient algorithm named Apriori-
itemsets, Neural Network..
                                                                         Feed Forward(AFF) based on Apriori algorithm and Feed
                                                                         Forward Neural Network is proposed, this algorithm can
                         I. INTRODUCTION
                                                                         efficiently combine the advantages of Apriori algorithm and
   Data mining has recently attracted considerable attention             Structure of Neural Network. Computational results verify the
from database practitioners and researchers because it has               good performance of the Apriori-Feed Forward(AFF)
been applied to many fields such as market strategy, financial           algorithm. The organization of this paper is as follows. In
forecasts and decision support [1]. Many algorithms have been            Section II, we will briefly review the Apriori method and Feed
proposed to obtain useful and invaluable information from                Forward Neural Network method. Section III proposes an
huge databases [2]. One of the most important algorithms is              efficient Apriori-Feed Forward(AFF) algorithm that based on
mining association rules, which was first introduced in [3,              Apriori and the Feed Forward(AFF) structure. Experimental
4].Association rule mining has many important applications in            results will be presented in Section IV. Section V gives out the
our life. An association rule is of the form X => Y. And each            conclusions.
rule has two measurements: support and confidence. The
association rule mining problem is to find rules that satisfy
user-specified minimum support and minimum confidence. It                 II. CLASSICAL MINING ALGORITHM AND NEURAL NETWORK
mainly includes two steps: first, find all frequent patterns;
second, generate association rules through frequent patterns.              A. Apriori Algorithm
Many algorithms for mining association rules from                        In [4], Agrawal proposed an algorithm called Apriori to the
transactions database have been proposed [5, 6, 7]since                  problem of mining association rules first. Apriori algorithm is
Apriori algorithm was first presented. However, most                     a bottm-up, breadth-first approach. The frequent itemsets are
algorithms were based on Apriori algorithm which generated               extended one item at a time.Its main idea is to generate k-th
and tested candidate itemsets iteratively. This may scan                 candidate itemsets from the (k-1)-th frequent itemsets and to

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                                                                                                    ISSN 1947-5500
                                                            (IJCSIS) International Journal of Computer Science and Information Security,
                                                                                                            Vol. 8, No.8, November 2010
find the k-th frequent itemsets from the k-th candidate                  structure. Through training data mining, the neural network
itemsets.The algorithm terminates when frequent itemsets can             method gradually calculates (including repeated iteration or
not be extended any more. But it has to generate a large                 cumulative calculation) the weights the neural network
amount of candidate itemsets and scans the data set as many              connected. The neural network model can be broadly divided
times as the length of the longest frequent itemsets. Apriori            into the following three types:
algorithm can be written by pseudocode as follows.                       (1) Feed-forward networks: it regards the perception back-
   Procedure Apriori, Input: data set D, minimum support                 propagation model and the function network as
minsup, Output: frequent itemsets L                                      representatives, and mainly used in the areas such as
(1) 1 L = find_frequent_1_itemsets(D);                                   prediction and pattern recognition;
(2) for (k = 2; Lk 1 −≠ ф; k++)                                         (2) Feedback network: it regards Hopfield discrete model and
(3) {                                                                    continuous model as representatives, and mainly used for
(4) Ck = Apriori_gen( Lk −1 , minsup);                                   associative memory and optimization calculation;
(5) for each transactions t _ D                                          (3) Self-organization networks: it regards adaptive resonance
(6) {                                                                    theory (ART) model and Kohonen model as representatives,
(7) Ct = subset( Ck , t);                                                and mainly used for cluster analysis.
(8) for each candidate c _Ct
(9) c.count++;                                                           D. Feedforward Neural Network :
(10) }                                                                   Feedforward neural network (FF network) are the most
(11) Lk = {c _Ck | c.count > minsup};                                    popular and most widely used models in many practical
(12) }                                                                   applications. They are known by many different names, such
(13) return L = { L1 _ L2 _ ... _ Ln };                                  as "multi-layer perceptrons."
   In the above pseudocode, Ck means k-th candidate itemsets                Figure 2(a) illustrates a one-hidden-layer FF network with
and Lk means k-th frequent itemsets.                                     inputs     ,...,  and output . Each arrow in the figure
    B. Neural Network                                                    symbolizes a parameter in the network. The network is divided
   Neural network[19,20] is a parallel processing network                into layers. The input layer consists of just the inputs to the
which generated with simulating the image intuitive thinking             network. Then follows a hidden layer, which consists of any
of human, on the basis of the research of biological neural              number of neurons, or hidden units placed in parallel. Each
network, according to the features of biological neurons and             neuron performs a weighted summation of the inputs, which
neural network and by simplifying, summarizing and refining.             then passes a nonlinear activation function , also called the
It uses the idea of non-linear mapping, the method of parallel           neuron function.
processing and the structure of the neural network itself to
express the associated knowledge of input and output.
Initially, the application of the neural network in data mining
was not optimistic, and the main reasons are that the neural
network has the defects of complex structure, poor
interpretability and long training time. But its advantages such
as high affordability to the noise data and low error rate, the
continuously advancing and optimization of various network
training algorithms, especially the continuously advancing and
                                                                         Figure 2(a) A feedforward network with one hidden layer and
improvement of various network pruning algorithms and rules
                                                                         one output.
extracting algorithm, make the application of the neural
network in the data mining increasingly favored by the
overwhelming majority of users.                                          Mathematically the functionality of a hidden neuron is
                                                                         described by
C. Neural Network Method in Data Mining
    There are seven common methods and techniques of data
mining[21,22,23] which are the methods of statistical analysis,
                                                                         where the weights {     ,   } are symbolized with the arrows
rough set, covering positive and rejecting inverse cases,
formula found, fuzzy method, as well as visualization                    feeding into the neuron.The network output is formed by
technology. Here, we focus on neural network method. Neural              another weighted summation of the outputs of the neurons in
network method is used for classification, clustering, feature           the hidden layer. This summation on the output is called the
mining, prediction and pattern recognition. It imitates the
                                                                         output layer. In Figure 2(a) there is only one output in the
neurons structure of animals, bases on the M-P model and
Hebb learning rule, so in essence it is a distributed matrix             output layer since it is a single-output problem. Generally, the

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                                                                                                     ISSN 1947-5500
                                                            (IJCSIS) International Journal of Computer Science and Information Security,
                                                                                                            Vol. 8, No.8, November 2010
number of output neurons equals the number of outputs of the                             Figure 2(b)
approximation problem. The neurons in the hidden layer of the                    III. APRIORI- FEEDFORWARD ALGORITHM(AFF)
network in Figure 2(a) are similar in structure to those of the          In this Section, a new algorithm based on Apriori and the
perceptron, with the exception that their activation functions           Feedforward Neural Network structure is presented, which is
                                                                         called Apriori- Feedforward Algorithm(AFF).Fig.3a shows the
can be any differential function. The output of this network is
                                                                         database structure in which there are different Item Ids and
given by                                                                 sets of Items purchased against Item ID and Fig 3(a)

                                                                                     Item_ID           Items
                                                                                     001               I1, I2, I3
                                                                                     002               I1, I3, I4
where n is the number of inputs and nh is the number of
                                                                                     003               I2, I4
neurons in the hidden layer. The variables {    ,   ,   , } are                      004               I1, I2
the parameters of the network model that are represented                             005               I1, I2, I3, I5
collectively by the parameter vector . In general, the neural                        ----              ------
network model will be represented by the compact notation                   Fig 3(a): Item Id and Item List of Database
g( ,x) whenever the exact structure of the neural network is not
necessary in the context of a discussion. Note that the size of
the input and output layers are defined by the number of inputs                     I1       f1
                                                                                                                  I1I2   f12
and outputs of the network and, therefore, only the number of
hidden neurons has to be specified when the network is                              I2       f2
                                                                                                                  I1I3   f13
defined. The network in Figure 2(a) is sometimes referred to
as a three-layer network, counting input, hidden, and output                        I3       f3
layers. However, since no processing takes place in the input
layer, it is also sometimes called a two-layer network. To
avoid confusion this network is called a one-hidden-layer FF
network throughout this documentation.                                   FIG 3(B): Data Structure of Nodes in FeedForward Neural
In training the network, its parameters are adjusted
incrementally until the training data satisfy the desired                The Apriori- Feedforward algorithm mainly includes two
mapping as well as possible; that is, until ( ) matches the              steps.
                                                                         First, a neural network model is prepared according to the
desired output y as closely as possible up to a maximum                  maximum number of items present in the dataset. Then first
number of iterations.                                                    transaction of the data set is scanned to find out the frequent 1
                                                                         itemsets, and then neural network is updated for frequent 2
The nonlinear activation function in the neuron is usually               itemsets frequent 3 itemsets and so on. The data set is scanned
chosen to be a smooth step function. The default is the                  only once to build all frequent combinations of datasets.
standard sigmoid                                                         While updating frequent 2/frequent 3 itemsets…, its pruning is
                                                                         done at the same time to avoid redundancy of item sets. At
                                                                         last, the built Neural Network is mined by Apriori-
                                                                         FeedForward Algorithm. The detailed Apriori-FeedForward
  that looks like this.                                                  Algorithm is as follows.

                                                                         Procedure : Create_Model
                                                                         Input: data set D, minimum support minsup
                                                                         (1) procedure Create_Model(n)
                                                                         (2) for(i=1;i ≠ ; i++)
                                                                         (3) for each itemset l1 ∈ lk-1
                                                                         (4) for each itemset l2 ∈ lk-1
                                                                         (5)          if( l1[1] = l2[1]) ( l1[2] = l2[2])          ( l1[3] = l2[3])
                                                                         …... ( l1[n] = l2[n])

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                                                                                                         ISSN 1947-5500
                                                             (IJCSIS) International Journal of Computer Science and Information Security,
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(6) then
(7)      C = l1 x l2
(8) if already_generated(l1 x l2) then
(9)      delete C
(10) else add C to Ck
(11) FNN(Ck)

Procedure FNN(Ck)
Input: itemset Model Ck
Output: frequent itemsets L
(1) procedure FNN(Ck)
(2) n = recordcount(Dataset)                                                                          Fig.4(b).
(3) for(i=1; i<n ; i++)                                                  From Fig.4(a), 4(b). we can make the following two
(4) {                                                                    statements. First, Apriori- FeedForward algorithm works much
(5) L1 = get_first_transaction(Dataset)                                  faster than Apriori. It uses a different method FNN to calculate
(6) upf = update_frequecy(l1 x l2)                                       the support of candidate itemsets and it consumes less memory
(7) if (upf >= min_sup)                                                  than Apriori because it doesn’t need to traverse database again
(8) print(l1 x l2)                                                       and again. It needs only single scan to the database.

In this algorithm a complete Feed forward neural network is
prepared according to the maximum number of items present                                 V. CONCLUSION AND FUTURE WORK
in the datasets. First layer of the network is a frequent 1              In this paper, we have proposed the Apriori- FeedForward
itemsets second layer is frequent 2 item sets and so on until a          algorithm. This method builds Feed Forward Neural Network
final layer is prepared which is a single node comprising of all         Model and scans the data base only once to generate frequent
items present in the datasets. Every n+1 layer is combination            patterns. The future work is to further improve the Apriori-
of item n with respect to all other items present at that layer,         Feed Forward algorithm and test more and larger datasets.
these layers are generated by calculating factorial of n+1
items.                                                                   .

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