I tried the following :
typedef std::tr1::unordered_map <Point2f,int> hash;
hash ht;
Point2f points;
points.x = ......
points.y = ......
.
.
.
ht.insert(hash::value_type(points,frame_num));
but I get the following error :
error: undefined reference to `std::tr1::hash<cv::Point_<float> >::operator()(cv::Point_<float>) const'
The whole reason for doing this is storing the place (coordinates as keys of the hash table) and the time (or frame number as values) of mass centers (points) as they happen! any help or suggestion is appreciated.