## 3 Materials and Methods
### Adapted BPSO Algorithm for Feature Selection in the Case of DLAs Sensors Data
Moreover, the number of returned features was restricted to six in the case of GA, DE, and BPSO, using the heuristic for features ranking introduced in this article that returns the results presented in Appendix A. In Table 5, the running times for each feature selection approach are presented. The running time of BPSO is much better than the running time of BFE, GA and DE, but slightly worse than the running time of FFS and comparable to the running time of RF. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Subject** & \(t_{m}\) & \(f_{m}\) & \(NRF_{m}\) & \(a_{m}\) \\ \hline \(S_{1}\) & 684,476 & 0.818 & 8 & 91.0\% \\ \(S_{2}\) & 910,064 & 0.806 & 6 & 93.7\% \\ \(S_{3}\) & 739,985 & 0.795 & 7 & 92.4\% \\ \(S_{4}\) & 714,869 & 0.799 & 7 & 90.0\% \\ \(S_{5}\) & 726,932 & 0.811 & 7 & 90.4\% \\ \(S_{6}\) & 614,417 & 0.814 & 7 & 94.3\% \\ \(S_{7}\) & 733,800 & 0.796 & 5 & 86.0\% \\ \(S_{8}\) & 625,166 & 0.808 & 7 & 91.1\% \\ \(S_{9}\) & 665,925 & 0.800 & 7 & 93.3\% \\ \(S_{10}\) & 658,837 & 0.804 & 6 & 89.7\% \\ \(S_{11}\) & 761,430 & 0.802 & 7 & 88.2\% \\ \(S_{12}\) & 793,377 & 0.803 & 7 & 92.8\% \\ \(S_{13}\) & 802,259 & 0.798 & 7 & 92.1\% \\ \(S_{14}\) & 760,730 & 0.803 & 6 & 90.9\% \\ \(S_{15}\) & 813,828 & 0.811 & 7 & 90.7\% \\ \(S_{16}\) & 885,900 & 0.805 & 7 & 91.0\% \\ \(S_{17}\) & 875,175 & 0.798 & 6 & 92.7\% \\ \(S_{18}\) & 774,223 & 0.793 & 7 & 91.1\% \\ \(S_{19}\) & 753,161 & 0.798 & 6 & 91.7\% \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Summary of the adapted BPSO algorithm mean results for each monitored subject. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Subject/Features Selection** & **FFS** & **BFE** & **RF** & **BPSO** & **GA** & **DE** \\ \hline \(S_{1}\) & 333,842 & 2,517,009 & 914,742 & 636,930 & 1,930,886 & 1,282,519 \\ \(S_{2}\) & 409,865 & 5,253,360 & 1,117,351 & 953,376 & 2,213,781 & 1,519,955 \\ \(S_{3}\) & 333,872 & 3,661,512 & 800,075 & 799,151 & 1,766,370 & 1,271,330 \\ \(S_{4}\) & 337,070 & 4,481,319 & 751,205 & 716,961 & 1,787,177 & 1,269,005 \\ \(S_{5}\) & 348,089 & 1,632,155 & 886,658 & 703,276 & 1,836,603 & 1,316,106 \\ \(S_{6}\) & 309,679 & 1,569,169 & 680,149 & 658,894 & 1,613,077 & 1,146,485 \\ \(S_{7}\) & 368,906 & 1,704,399 & 827,109 & 705,606 & 1,882,546 & 1,373,507 \\ \(S_{8}\) & 326,191 & 1,540,248 & 863,979 & 588,280 & 1,663,440 & 1,207,692 \\ \(S_{9}\) & 349,503 & 4,865,604 & 723,893 & 652,314 & 1,791,708 & 1,282,526 \\ \(S_{10}\) & 345,890 & 3,366,558 & 695,436 & 575,586 & 1,750,748 & 1,285,746 \\ \(S_{11}\) & 329,980 & 2,669,384 & 814,888 & 822,193 & 1,733,939 & 1,255,230 \\ \(S_{12}\) & 342,686 & 1,580,970 & 830,055 & 868,976 & 1,832,432 & 1,319,197 \\ \(S_{13}\) & 336,975 & 4,311,050 & 905,903 & 849,842 & 1,855,374 & 1,294,919 \\ \(S_{14}\) & 333,746 & 3,019,609 & 902,391 & 892,880 & 1,761,730 & 1,253,549 \\ \(S_{15}\) & 326,056 & 3,081,598 & 873,733 & 915,939 & 1,648,931 & 1,233,069 \\ \(S_{16}\) & 349,341 & 3,455,577 & 1,109,170 & 931,524 & 1,838,868 & 1,303,958 \\ \(S_{17}\) & 322,297 & 1,534,359 & 730,817 & 664,468 & 1,715,616 & 1,287,910 \\ \(S_{18}\) & 318,742 & 5,478,390 & 715,003 & 875,047 & 1,644,804 & 1,157,746 \\ \(S_{19}\) & 319,628 & 4,515,086 & 782,075 & 675,779 & 1,662,081 & 1,141,452 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: The running time for forward feature selection (FFS), backward features elimination (BFE), random forest (RF), binary particle swarm optimization (BPSO), genetic algorithm (GA) and differential evolution (DE) for each monitored subject, in milliseconds. In Figure 4, the selected features for each feature selection approach are presented, namely FFS, BFE, RF, BPSO, GA, and DE, for each monitored subject. Comparison of the DLAs Classification Results Obtained Using the Adapted Version of BPSO with the Results Obtained Using Other Methods

In Table 6 the DLAs classification results for each feature selection approach are presented, when the applied classification algorithm is RF. For eight out of the 19 monitored subjects, BPSO returns classification results that are from the top three results.