# Eye State Identification Based on Discrete Wavelet Transforms
## 5 Experimental Results
### Scheme 2: Two Features
The second set of experiments are used to determine the performance of using one or two sensors for short delays. Figure 9 depicts the accuracy obtained for each subject and ocular state as a function of the window size. As in previous experiments, the overlapped time slot \(d\) was selected to be 80% of the window size \(D\); therefore, the delay in the response will be 20% of \(D\). As occurred in Scheme 1, there exists a trade-off between the window size and the accuracy of the system, i.e., as window size increases the obtained accuracy improves and vice versa. Furthermore, the results obtained with the data from one sensor or two sensors are very close for large window sizes. However, in some subjects, such as Subjects 1, 3 and 5 (Figure 9a,c,e), the accuracy obtained for short window duration with two sensors is higher than the one obtained only with one sensor. This can also be seen in Figure 9h, which depicts the average accuracy for all the subjects. Here, we can clearly observe that, for short window sizes, the data from two sensors offer better accuracy rates. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Wavelet**} & \multirow{2}{*}{**Filter Length**} & \multicolumn{2}{c}{**Closed**} & \multicolumn{2}{c}{**Open**} \\ \cline{3-6}  & & **O1 and O2 (\%)** & **O2 (\%)** & **O1 and O2 (\%)** & **O2 (\%)** \\ \hline db2 & 4 & 93.49 & 91.31 & 98.29 & 96.57 \\ db4 & 8 & 94.06 & 92.80 & 98.86 & **97.71** \\ db8 & 16 & **94.40** & **93.83** & **99.31** & 97.60 \\ coif1 & 6 & 93.71 & 92.91 & 98.17 & 96.80 \\ coif4 & 24 & **94.40** & 93.71 & 99.09 & 97.49 \\ haar & 2 & 93.37 & 91.54 & 97.94 & 96.11 \\ sym2 & 4 & 93.49 & 91.31 & 98.29 & 96.57 \\ sym4 & 8 & 93.94 & 93.03 & 98.06 & 97.03 \\ sym10 & 20 & **94.40** & 93.03 & 98.63 & 97.37 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Average accuracy (in %) of all the subjects obtained for each wavelet type and ocular state for one and two sensor data using Scheme 2. Bold values indicate the highest value of each column. Filter length column represents the number of filter coefficients employed for the multi-resolution analysis. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Subject**} & \multicolumn{2}{c}{**Closed**} & \multicolumn{2}{c}{**Open**} \\ \cline{2-5}  & **O1 and O2 (\%)** & **O2 (\%)** & **O1 and O2 (\%)** & **O2 (\%)** \\ \hline
1 & 100.00 & 100.00 & 100.00 & 100.00 \\
2 & 84.00 & 80.00 & 96.00 & 89.60 \\
3 & 100.00 & 100.00 & 100.00 & 96.00 \\
4 & 95.20 & 95.20 & 100.00 & 100.00 \\
5 & 93.60 & 95.20 & 100.00 & 100.00 \\
6 & 92.00 & 91.20 & 100.00 & 98.40 \\
7 & 96.00 & 95.20 & 99.20 & 99.20 \\ \hline Mean & 94.40 & 93.83 & 99.31 & 97.60 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Average accuracy (in %) obtained for each subject and ocular state for one and two sensor data using Scheme 2, db8 as mother wavelet, a window duration of 10 s and a delay of \(D-d=2\) s.  
Figure 9: Accuracy obtained for each subject as a function of the window size using Scheme 2. Figures (**a**–**g**) represent the accuracy for Subjects 1 to 7. Figure (**h**) shows the average accuracy of all the subjects.