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improving music mood classification using lyrics, audio and social tags

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<strong>music</strong> <strong>mood</strong> <strong>classification</strong> which involves dozens of <strong>mood</strong> categories. Previous experiments on<br />

automatic <strong>music</strong> <strong>mood</strong> <strong>classification</strong> usually considered only a h<strong>and</strong>ful of <strong>mood</strong> categories which<br />

likely simplified the real problem. However, in <strong>music</strong> <strong>mood</strong> <strong>classification</strong>, when the number of<br />

categories gets bigger than 10, the performances of multi-class <strong>classification</strong> algorithms become<br />

very low <strong>and</strong> lose their practical value (Li & Ogihara, 2004). Second, multi-class <strong>classification</strong> is<br />

usually adopted for experiments where the number of instances in each category is equal.<br />

However, in order to maximize the usage of the available <strong>audio</strong> <strong>and</strong> <strong>lyrics</strong> data, the experiment<br />

dataset in this dissertation research contains different number of instances in each category (see<br />

Section 5.2).<br />

4.1.2 Performance Measure <strong>and</strong> Statistical Test<br />

Commonly used performance measures for <strong>classification</strong> problems include accuracy,<br />

precision, recall <strong>and</strong> F-measure. Table 4.1 shows a contingency table of a binary prediction.<br />

Compared to the ground truth, a prediction can be the following: true positive (TP): the<br />

prediction <strong>and</strong> truth are both positive; false negative (FN): the prediction is negative but the truth<br />

is positive; false positive (FP): the prediction is positive but the truth is negative; <strong>and</strong> true<br />

negative (TN): the prediction <strong>and</strong> truth are both negative.<br />

Table 4.1 Contingency table of binary <strong>classification</strong> results<br />

Ground truth<br />

Prediction<br />

Positive Negative<br />

Positive True positive False negative<br />

Negative False positive True negative<br />

The performance measures are defined as follows:<br />

47

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