771 research outputs found
New probabilistic interest measures for association rules
Mining association rules is an important technique for discovering meaningful
patterns in transaction databases. Many different measures of interestingness
have been proposed for association rules. However, these measures fail to take
the probabilistic properties of the mined data into account. In this paper, we
start with presenting a simple probabilistic framework for transaction data
which can be used to simulate transaction data when no associations are
present. We use such data and a real-world database from a grocery outlet to
explore the behavior of confidence and lift, two popular interest measures used
for rule mining. The results show that confidence is systematically influenced
by the frequency of the items in the left hand side of rules and that lift
performs poorly to filter random noise in transaction data. Based on the
probabilistic framework we develop two new interest measures, hyper-lift and
hyper-confidence, which can be used to filter or order mined association rules.
The new measures show significantly better performance than lift for
applications where spurious rules are problematic
An efficient closed frequent itemset miner for the MOA stream mining system
Mining itemsets is a central task in data mining, both in the batch and the streaming paradigms. While robust, efficient, and well-tested implementations exist for batch mining, hardly any publicly available equivalent exists for the streaming scenario. The lack of an efficient, usable tool for the task hinders its use by practitioners and makes it difficult to assess new research in the area. To alleviate this situation, we review the algorithms described in the literature, and implement and evaluate the IncMine algorithm by Cheng, Ke, and Ng (2008) for mining frequent closed itemsets from data streams. Our implementation works on top of the MOA (Massive Online Analysis) stream mining framework to ease its use and integration with other stream mining tasks. We provide a PAC-style rigorous analysis of the quality of the output of IncMine as a function of its parameters; this type of analysis is rare in pattern mining algorithms. As a by-product, the analysis shows how one of the user-provided parameters in the original description can be removed entirely while retaining the performance guarantees. Finally, we experimentally confirm both on synthetic and real data the excellent performance of the algorithm, as reported in the original paper, and its ability to handle concept drift.Postprint (published version
Efficient Discovery of Association Rules and Frequent Itemsets through Sampling with Tight Performance Guarantees
The tasks of extracting (top-) Frequent Itemsets (FI's) and Association
Rules (AR's) are fundamental primitives in data mining and database
applications. Exact algorithms for these problems exist and are widely used,
but their running time is hindered by the need of scanning the entire dataset,
possibly multiple times. High quality approximations of FI's and AR's are
sufficient for most practical uses, and a number of recent works explored the
application of sampling for fast discovery of approximate solutions to the
problems. However, these works do not provide satisfactory performance
guarantees on the quality of the approximation, due to the difficulty of
bounding the probability of under- or over-sampling any one of an unknown
number of frequent itemsets. In this work we circumvent this issue by applying
the statistical concept of \emph{Vapnik-Chervonenkis (VC) dimension} to develop
a novel technique for providing tight bounds on the sample size that guarantees
approximation within user-specified parameters. Our technique applies both to
absolute and to relative approximations of (top-) FI's and AR's. The
resulting sample size is linearly dependent on the VC-dimension of a range
space associated with the dataset to be mined. The main theoretical
contribution of this work is a proof that the VC-dimension of this range space
is upper bounded by an easy-to-compute characteristic quantity of the dataset
which we call \emph{d-index}, and is the maximum integer such that the
dataset contains at least transactions of length at least such that no
one of them is a superset of or equal to another. We show that this bound is
strict for a large class of datasets.Comment: 19 pages, 7 figures. A shorter version of this paper appeared in the
proceedings of ECML PKDD 201
Mining Frequent Itemsets over Uncertain Databases
In recent years, due to the wide applications of uncertain data, mining
frequent itemsets over uncertain databases has attracted much attention. In
uncertain databases, the support of an itemset is a random variable instead of
a fixed occurrence counting of this itemset. Thus, unlike the corresponding
problem in deterministic databases where the frequent itemset has a unique
definition, the frequent itemset under uncertain environments has two different
definitions so far. The first definition, referred as the expected
support-based frequent itemset, employs the expectation of the support of an
itemset to measure whether this itemset is frequent. The second definition,
referred as the probabilistic frequent itemset, uses the probability of the
support of an itemset to measure its frequency. Thus, existing work on mining
frequent itemsets over uncertain databases is divided into two different groups
and no study is conducted to comprehensively compare the two different
definitions. In addition, since no uniform experimental platform exists,
current solutions for the same definition even generate inconsistent results.
In this paper, we firstly aim to clarify the relationship between the two
different definitions. Through extensive experiments, we verify that the two
definitions have a tight connection and can be unified together when the size
of data is large enough. Secondly, we provide baseline implementations of eight
existing representative algorithms and test their performances with uniform
measures fairly. Finally, according to the fair tests over many different
benchmark data sets, we clarify several existing inconsistent conclusions and
discuss some new findings.Comment: VLDB201
A Framework for High-Accuracy Privacy-Preserving Mining
To preserve client privacy in the data mining process, a variety of
techniques based on random perturbation of data records have been proposed
recently. In this paper, we present a generalized matrix-theoretic model of
random perturbation, which facilitates a systematic approach to the design of
perturbation mechanisms for privacy-preserving mining. Specifically, we
demonstrate that (a) the prior techniques differ only in their settings for the
model parameters, and (b) through appropriate choice of parameter settings, we
can derive new perturbation techniques that provide highly accurate mining
results even under strict privacy guarantees. We also propose a novel
perturbation mechanism wherein the model parameters are themselves
characterized as random variables, and demonstrate that this feature provides
significant improvements in privacy at a very marginal cost in accuracy.
While our model is valid for random-perturbation-based privacy-preserving
mining in general, we specifically evaluate its utility here with regard to
frequent-itemset mining on a variety of real datasets. The experimental results
indicate that our mechanisms incur substantially lower identity and support
errors as compared to the prior techniques
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