# Action Classification for Partially Occluded Silhouettes by Means of Shape and Action Descriptors
## 4 Experimental Conditions and Results
For the other subgroup, an accuracy of 84.44% is achieved in three experiments using area, shorterMBR and rectangularity. However, if rectangularity is employed, the representation size is smaller (46 coefficients using C1 correlation). \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Shape Descriptor** & \multicolumn{2}{c}{**Actions Performed in Place**} & \multicolumn{2}{c}{**Actions with Changing Location of a Silhouette**} \\  & **EU** & **C1** & **EU** & **C1** \\ \hline Rectangularity & 68.89\% & 71.11\% & 68.89\% & 73.33\% \\  & (68) & (110) & (79) & (84) \\ \hline Elongation & 91.11\% & 91.11\% & 68.89\% & 64.44\% \\  & (57) & (55) & (79) & (39) \\ \hline Eccentricity & 71.11\% & 75.56\% & 64.44\% & 60.00\% \\  & (88) & (108) & (37) & (38) \\ \hline Width & 82.22\% & 84.44\% & 55.56\% & 60.00\% \\  & (54) & (54) & (17) & (57) \\ \hline Length & 62.22\% & 62.22\% & 64.44\% & 60.00\% \\  & (41) & (18) & (36) & (65) \\ \hline Area & 68.89\% & 71.11\% & 62.22\% & 64.44\% \\  & (39) & (106) & (66) & (70) \\ \hline LongerMBR & 68.89\% & 71.11\% & 66.67\% & 66.67\% \\  & (41) & (41) & (68) & (89) \\ \hline ShorterMBR & 88.89\% & 84.44\% & 71.11\% & 73.33\% \\  & (55) & (56) & (30) & (71) \\ \hline Perimeter & 77.78\% & 80.00\% & 66.67\% & 62.22\% \\  & (52) & (52) & (40) & (39) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Results for the experiments using the ‘lower-occlusion’ database. Correct classification rates are given for coarsely classified actions, nine shape descriptors based on the Minimum Bounding. Rectangle and two matching measures (EU—distance, C1—correlation). The number of the DFT coefficients is given in brackets. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Shape Descriptor** & \multicolumn{2}{c}{**Actions Performed in Place**} & \multicolumn{2}{c}{**Actions with Changing Location of a Silhouette**} \\  & **EU** & **C1** & **EU** & **C1** \\ \hline Rectangularity & 77.78\% & 75.56\% & 82.22\% & 84.44\% \\  & (55) & (50) & (28) & (46) \\ \hline Elongation & 82.22\% & 88.89\% & 82.22\% & 80.00\% \\  & (47) & (51) & (27) & (28) \\ \hline Eccentricity & 68.89\% & 71.11\% & 73.33\% & 77.78\% \\  & (32) & (34) & (41) & (168) \\ \hline Width & 73.33\% & 71.11\% & 60.00\% & 60.00\% \\  & (53) & (81) & (39) & (18) \\ \hline Length & 55.56\% & 64.44\% & 75.56\% & 75.56\% \\  & (38) & (42) & (40) & (68) \\ \hline Area & 68.89\% & 75.56\% & 84.44\% & 77.78\% \\  & (38) & (83) & (70) & (38) \\ \hline LongerMBR & 75.56\% & 80.00\% & 60.00\% & 60.00\% \\  & (53) & (58) & (27) & (40) \\ \hline ShorterMBR & 80.00\% & 80.00\% & 82.22\% & 84.44\% \\  & (124) & (65) & (18) & (69) \\ \hline Perimeter & 68.89\% & 68.89\% & 75.56\% & 75.56\% \\  & (99) & (56) & (93) & (75) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Results for the experiments using the ‘upper-occlusion’ database. Correct classification rates are given for coarsely classified actions, nine shape descriptors based on the Minimum Bounding. Rectangle and two matching measures (EU—distance, C1—correlation). The number of the DFT coefficients is given in brackets. The proposed approach is also tested using the Weizmann database without any occlusions. The comparison of the experimental results yielding the highest classification accuracy is given in Table 3. Some conclusions can be drawn. Firstly, in several cases, the use of C1 correlation gives better results or the results are equal to the experiments with Euclidean distance. Secondly, in the subgroup of actions with changing location of a silhouette, the lower occlusion has stronger influence on the results. It can be concluded that, for action classification purposes, the information about feet positions is more important than the presence of head and shoulders. It is also confirmed by the results obtained for the 'upper-occlusion' database, which were very similar to those achieved on the unoccluded database. Different conclusions can be drawn from the results obtained for actions performed in place.