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We explore in this paper a novel sampling algorithm, referred to as algorithm PAS (standing for Proportion Approximation Sampling), to generate a high-quality online sample with the desired sample rate. The sampling quality refers to the consistency between the population proportion and the sample proportion of each categorical value in the database. Note that the state-of-the-art sampling algorithm to preserve the sampling quality has to examine the population proportion of each categorical value in a pilot sample a priori and is thus not applicable to incremental mining applications. To remedy this, algorithm PAS adaptively determines the inclusion probability of each incoming tuple in such a way that the sampling quality can be sequentially preserved while also guaranteeing the sample rate close to the user specified one. Importantly, PAS not only guarantees the proportion consistency of each categorical value but also excellently preserves the proportion consistency of multivariate statistics, which will be significantly beneficial to various data mining applications. For better execution efficiency, we further devise an algorithm, called algorithm EQAS (standing for Efficient Quality-Aware Sampling), which integrates PAS and random sampling to provide the flexibility of striking a compromise between the sampling quality and the sampling efficiency. As validated in experimental results on real and synthetic data, algorithm PAS can stably provide high-quality samples with corresponding computational overhead, whereas algorithm EQAS can flexibly generate samples with the desired balance between sampling quality and sampling efficiency. In addition, while applying the sample generated by algorithms PAS and EQAS to incremental mining applications, a significant efficiency improvement can be obtained without compromising the resulting precision, showing the prominent advantage of both proposed algorithms to be the quality-aware sampling means for incremental mining applications.
Sequential sampling, incremental data mining.

K. Chuang, K. Lin and M. Chen, "Quality-Aware Sampling and Its Applications in Incremental Data Mining," in IEEE Transactions on Knowledge & Data Engineering, vol. 19, no. , pp. 468-484, 2007.
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