modification of clustering: the parameter of clustering(euclidean distance between points) has been changed from 1cm into 0.5 cm, and it can be seen that some noise are reduced especially for the box of 11 frames. 

The method of the entropy calculation is as discussed (using d=1mm, every time grouping the points which has the distance of 0-d/3,  d/3-2d/3,  2d/-d to the shifting plane on two sides respectively, and then calculate the p1,p2,p3 and entropy). The graphics below show the entropy by using this method for box1 with 11 frames and 1 frame, box2 with 11 frames and 1 frame.  The x axis represents x(mm), y represents the entropy. And the real length of the boxes are both 14.5 cm. d is equal to 0.001 (m), counting the number of points in blue region(N1), green region(N2) and red region(N3).