OpenCV- Working with OpenCV

class atsKalman { public:     atsKalman()     {         KalmanFilter KF(4, 2, 0);         Mat_<float> state(4, 1); /* (x, y, Vx, Vy) */         Mat processNoise(4, 1, CV_32F);         Mat_<float> measurement(2,1);         measurement.setTo(Scalar(0));         KFs = KF;         measurements = measurement;     }     void setKalman(int x, int y)     {         KFs.statePre.at<float>(0) = x;         KFs.statePre.at<float>(1) = y;         KFs.statePre.at<float>(2) = 0;         KFs.statePre.at<float>(3) = 0;       ...