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improving music mood classification using lyrics, audio and social tags

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6.4.3 Analysis of Text Stylistic Features<br />

As shown in the results, TextStyle is a very interesting feature type. It captures very different<br />

characteristics from the <strong>lyrics</strong> than other feature types, i.e., TextStyle is orthogonal to other<br />

feature types. This subsection takes a closer look at TextStyle to determine the most important<br />

features within this type.<br />

The specific features in TextStyle are listed in Table 6.2. The interjection words <strong>and</strong><br />

punctuation marks were selected <strong>using</strong> a series of experiments. Classification performances<br />

<strong>using</strong> varied numbers of top-ranked features are compared in Table 6.7, with the row of best<br />

performances marked as bold.<br />

Table 6.7 Feature selection for TextStyle<br />

Number of features<br />

Accuracy<br />

TextStats I&P Total TextStyle ANEW+TextStyle<br />

17 0 17 0.524 0.634<br />

17 8 25 0.529 0.637<br />

17 15 32 0.526 0.632<br />

17 25 42 0.514 0.631<br />

17 45 62 0.514 0.628<br />

17 75 92 0.513 0.615<br />

17 134 151 0.513 0.612<br />

Initially all common punctuation marks <strong>and</strong> interjection words 16 were considered. There are<br />

134 of them. Then the interjection words <strong>and</strong> punctuation marks (denoted as “I&P” in Table 6.7)<br />

were ranked according to their SVM weights (see below), <strong>and</strong> the n most important ones were<br />

16 The list of English interjection words was based on the one obtained from http://www.english-grammarrevolution.com/list-of-interjections.html<br />

84

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