x=np.linspace(0,2*math.pi,n) n=len(x) r=int(math.ceil(f*n)) h=[np.sort(np.abs(x-x[i]))[r] for i in range(n)] this is part of a python code. the last line is confusing? x is a matrix and x[i] is a number. how calculate x-x[i] for each i? why the put r in [] ?