getAdj_manual.Rdan efficient function to find the neighbors based on the matrix of position and a pre-defined radius.
getAdj_manual(pos, radius)is a n-by-d matrix of position, where n is the number of spots, and d is the dimension of coordinates.
is a threashold of Euclidean distance to decide whether a spot is an neighborhood of another spot. For example, if the Euclidean distance between spot A and B is less than radius, then A is taken as the neighbourhood of B.
A sparse matrix containing the neighbourhood