Confidence value of measurement
d = distance(obj, z_matrix)
d = distance(obj, z_matrix) computes a distance between the location of a detected object and the predicted location by the Kalman filter object. Each row of the N-column z_matrix input matrix contains a measurement vector. The distance method returns a row vector where each distance element corresponds to the measurement input.
This distance computation takes into account the covariance of the predicted state and the process noise. The distance method can only be called after the predict method.