dx = np.random.randn(100)
dy = np.random.randn(100)
x = np.cumsum(dx)
y = np.cumsum(dy)

x = np.zeros(100)
y = np.zeros(100)
for i in range(1, 100):
    x[i] = x[i-1] + np.random.randn()
    y[i] = y[i-1] + np.random.randn()