## 5 Results and Discussion
### Results of Approach 1
\begin{table}
\begin{tabular}{l c c c c c c c} \hline \hline \multicolumn{2}{c}{} & \multicolumn{2}{c}{**CI\_TL**} & \multicolumn{5}{c}{**CL\_RT**} \\ \hline \# & **CIs** & **Accuracy (\%)** & **Std** & \# & **CIs** & **Accuracy (\%)** & **Std** \\ \hline
1 & Zero crossing & 25.6 & 0.20 & 1 & SSC & 25.85 & 0.26 \\ \hline
2 & Wave length & 60.45 & 3.26 & 2 & SRAV & 54.74 & 3.63 \\ \hline
3 & Kurtosis & 76.63 & 2.04 & 3 & Wave length & 85.43 & 3.15 \\ \hline
4 & WAMP & 85.07 & 1.29 & 4 & WAMP & 87.21 & 1.32 \\ \hline
5 & SSC & 86.93 & 1.50 & 5 & Shape factor & 89.27 & 1.83 \\ \hline
6 & CPT4 & 89.69 & 1.12 & 6 & Skewness & 90.43 & 1.85 \\ \hline
7 & Skewness & **92.89** & 1.45 & 7 & Zero crossing & 93.65 & 2.46 \\ \hline
8 & Shape factor & 92.89 & 1.18 & 8 & Kurtosis & **95.17** & 1.30 \\ \hline
9 & CPT3 & 92 & 1.61 & 9 & Energy operator & 94.64 & 0.93 \\ \hline
10 & Energy operator & 91.64 & 0.74 & 10 & CPT3 & 94.36 & 1.38 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Top 10 CIs and accuracies average over time domain. In order to illustrate the importance of feature selection, a scatter plot obtained from the best case, related to the CI_FL set, is presented in Figure 6, where the class 1 is the red color, class 2 is the green color, class 3 is the cyan color, and class 4 is the violet color. This set provides the high accuracy and low \(std\) using 3 attributes. The formation of small clusters can be observed for each of the classes in different locations in the three-dimensional space, and no perfect boundaries are exhibited. However, these three attributes can provide over 80% of accuracy, according to Figure 5. \begin{table}
\begin{tabular}{l l c c c c c} \hline \hline  & \multicolumn{3}{c}{**CI\_FL**} & \multicolumn{5}{c}{**Cl\_FR**} \\ \hline \# & **CIs** & **Accuracy (\%)** & **Std** & **\#** & **CIs** & **Accuracy (\%)** & **Std** \\ \hline
1 & PKF & 25.6 & 0.15 & 1 & Skewnessf & 25.85 & 0.17 \\
2 & CP2 & 56.8 & 2.93 & 2 & Spectrum spread & 41.77 & 2.44 \\
3 & SM4 & 85.51 & 1.35 & 3 & PKF & 71.38 & 2.65 \\
4 & FR & 72 & 2.54 & 4 & CP2 & 82.75 & 3.13 \\
5 & Skewnessf & 79.03 & 2.57 & 5 & MDF & 83.99 & 2.48 \\
6 & Spectrum spread & 87.21 & 2.43 & 6 & FR & 89.36 & 1.58 \\
7 & VCF & **91.29** & 2.92 & 7 & CP3 & 94.01 & 1.16 \\
8 & Centroid of Spectrum & 90.4 & 2.82 & 8 & SM1 & 93.47 & 1.32 \\
9 & Kurtosisf & 90.13 & 1.08 & 9 & VCF & **94.36** & 0.93 \\
10 & Entropy of spectrum & 90.23 & 1.97 & 10 & Centroid of Spectrum & 94.27 & 1.70 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Top 10 features and accuracies average over frequency domain. \begin{table}
\begin{tabular}{l l c c c c c c} \hline \hline  & \multicolumn{3}{c}{**CI\_FL**} & \multicolumn{5}{c}{**CI\_FR**} \\ \hline \# & **CIs** & **Accuracy (\%)** & **Std** & **\#** & **CIs** & **Accuracy (\%)** & **Std** \\ \hline
1 & Zero crossing & Time & 25.6 & 0.15 & 1 & SSC & Time & 25.85 & 0.17 \\
2 & PKF & Freq & 52.8 & 1.33 & 2 & FR & Freq & 50.81 & 1.77 \\
3 & WAMP & Time & 73.43 & 3.37 & 3 & SM1 & Freq & 71.56 & 1.86 \\
4 & CP2 & Freq & 78.85 & 1.91 & 4 & Skewnessf & Freq & 88.56 & 1.88 \\
5 & SSC & Time & 82.49 & 1.89 & 5 & Spectrum spread & Freq & 93.83 & 1.67 \\
6 & Shape factor & Time & 92.62 & 1.70 & 6 & Zero crossing & Time & 95.26 & 1.19 \\
7 & Skewness & Time & 93.69 & 2.08 & 7 & SM4 & Freq & 94.63 & 1.15 \\
8 & Kurtosis & Time & 94.49 & 0.89 & 8 & CP3 & Freq & 96.87 & 0.55 \\
9 & SM4 & Freq & 94.4 & 2.35 & 9 & CP2 & Freq & 96.6 & 2.46 \\
10 & FR & Freq & **96.62** & 0.59 & 10 & PKF & Freq & **97.14** & 1.29 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Top 10 CIs and accuracies average over time and frequency domain.