INFORMATICA, 2016, Vol. 27, No. 2, 257–281 257 2016 Vilnius University DOI: http://dx.doi.org/10.15388/Informatica.2016.84 Fractal-Based Methods as a Technique for Estimating the Intrinsic Dimensionality of High-Dimensional Data: A Survey Rasa KARBAUSKAITE˙ ∗, Gintautas DZEMYDA Institute of Mathematics and Informatics, Vilnius University Akademijos 4, LT-08663, Vilnius, Lithuania e-mail:
[email protected],
[email protected] Received: December 2015; accepted: April 2016 Abstract. The estimation of intrinsic dimensionality of high-dimensional data still remains a chal- lenging issue. Various approaches to interpret and estimate the intrinsic dimensionality are deve- loped. Referring to the following two classifications of estimators of the intrinsic dimensionality – local/global estimators and projection techniques/geometric approaches – we focus on the fractal- based methods that are assigned to the global estimators and geometric approaches. The compu- tational aspects of estimating the intrinsic dimensionality of high-dimensional data are the core issue in this paper. The advantages and disadvantages of the fractal-based methods are disclosed and applications of these methods are presented briefly. Key words: high-dimensional data, intrinsic dimensionality, topological dimension, fractal dimension, fractal-based methods, box-counting dimension, information dimension, correlation dimension, packing dimension. 1. Introduction In real applications, we confront with data that are of a very high dimensionality. For ex- ample, in image analysis, each image is described by a large number of pixels of different colour. The analysis of DNA microarray data (Kriukien˙e et al., 2013) deals with a high dimensionality, too. The analysis of high-dimensional data is usually challenging.