“…Unsupervised classification has been investigated through numerous means (Turney, 2002;Lee et al, 2002a;van Zyl, 2002;Hegarat-Mascle et al, 2002;Ferro-Famil et al, 2002;Chaovalit and Zhou, 2005;Lee et al, 2002b;Gllavata et al, 2004;Phu et al, 2016;Phu et al, 2017a;2017b;2017c;2017d;2017e;2017f;2017g;2017h), such as a simple unsupervised learning algorithm to classify reviews as recommended or not recommended, which classified reviews according to the average semantic orientation of the phrases, specifically the adjectives and adverbs, used in the reviews (Hegarat-Mascle et al, 2002). In another study , the use of an imaging radar polarimeter data for unsupervised classification of scattering behavior was described by comparing the polarization properties of each pixel in an image to that of simple classes of scattering, such as even number of reflections, odd number of reflections, and diffuse scattering (van Zyl, 2002).…”