atlas.py 文件源码

def gen_adj_mat(longs, lats, prob_edge=.2,
                        additional_length=lambda: np.random.exponential(20,1)):
    '''Get an adjacency matrix for the cities whose longitudes and latitudes
    are passed. Each entry will either be a number somewhat greater than the
    crow-flies distance between the two cities (with probability prob_edge),
    or math.inf. The matrix will consist of floats, and be symmetric. The
    diagonal will be all zeroes. The "somewhat greater" is controlled by the
    additional_length parameter, a function returning a random amount.'''

    # Generate full nxn Bernoulli's, even though we'll only use the upper
    # triangle.
    edges = np.random.binomial(1, prob_edge, size=(len(longs),len(longs)))
    am = np.zeros((len(longs),len(longs)))
    for i in range(len(longs)):
        for j in range(len(longs)):
            if i==j:
                am[i,i] = 0
            elif i < j:
                if edges[i,j] == 1:
                    am[i,j] = (math.hypot(longs[i]-longs[j],lats[i]-lats[j])
                        + additional_length())
                    am[j,i] = am[i,j]
                else:
                    am[i,j] = am[j,i] = math.inf
    return np.around(am,1)