Question

Using Python: Exercise 2.5: Use a random number generator in Python (you can try numpy.random.choice, you will need to give it the two element array [-1,1]) to create several random walks, i.e. a lists of numbers where the Nth entry is the position of the robot after N steps with 100 total steps of length 1 and plot the position vs. step number. From looking at the random walks, discuss in words how the robot can move away from its initial position even though it has equal probability of moving in each direction.

Answer 1

>>> a = np.random.rand(4)              # uniform in [0, 1]
>>> a
array([ 0.58597729,  0.86110455,  0.9401114 ,  0.54264348])

>>> b = np.random.randn(4)             # gaussian
>>> b
array([-2.56844807,  0.06798064, -0.36823781,  0.86966886])

>>> c = np.random.rand(3, 3)
>>> c
array([[ 0.31976645,  0.64807526,  0.74770801],
       [ 0.8280203 ,  0.8669403 ,  0.07663683],
       [ 0.11527489,  0.11494884,  0.13503285]])

>>> d = np.random.zipf(1.5, size=(2, 8))  # Zipf distribution (s=1.5)
>>> d
array([[5290,    1,    6,    9,    1,    1,    1,    2],
       [   1,    5,    1,   13,    1,    1,    2,    1]])

>>> np.random.seed(1234)                  # Setting the random seed
>>> np.random.rand(3)
array([ 0.19151945,  0.62210877,  0.43772774])
>>> np.random.seed(1234)
>>> np.random.rand(5)
array([ 0.19151945,  0.62210877,  0.43772774,  0.78535858,  0.77997581])