uniform sample from d-ball

uniform_sample_dball.py

def uniformsample_dball(npoint, nd=2):
    # https://extremelearning.com.au/how-to-generate-uniformly-random-points-on-n-spheres-and-n-balls/
    # # method 20
    eps = 1e-12
    u = np.random.normal(0,1, (npoint,nd))
    norm = np.sum(u ** 2, axis=1) ** 0.5
    r = np.random.random(npoint)**(1.0/nd)
    x = (r / (norm+eps)).reshape((-1,1)) * u
    return x

def uniformsample_dball2(npoint, nd=2):
    # https://extremelearning.com.au/how-to-generate-uniformly-random-points-on-n-spheres-and-n-balls/
    # # method 22
    u = np.random.normal(0,1, (npoint,nd+2))
    norm = np.sum(u ** 2, axis=1) ** 0.5
    x = (u/norm.reshape((-1,1)))[:,:nd]
    return x