16. Multiple Measurements

Multiple Measurements

Question:

Start Quiz:

#Modify the code so that it updates the probability twice
#and gives the posterior distribution after both 
#measurements are incorporated. Make sure that your code 
#allows for any sequence of measurement of any length.

p=[0.2, 0.2, 0.2, 0.2, 0.2]
world=['green', 'red', 'red', 'green', 'green']
measurements = ['red', 'green']
pHit = 0.6
pMiss = 0.2

def sense(p, Z):
    q=[]
    for i in range(len(p)):
        hit = (Z == world[i])
        q.append(p[i] * (hit * pHit + (1-hit) * pMiss))
    s = sum(q)
    for i in range(len(q)):
        q[i] = q[i] / s
    return q
#
#ADD YOUR CODE HERE
#
print p

User's Answer:

(Note: The answer done by the user is not guaranteed to be correct)

#Modify the code so that it updates the probability twice
#and gives the posterior distribution after both 
#measurements are incorporated. Make sure that your code 
#allows for any sequence of measurement of any length.

p=[0.2, 0.2, 0.2, 0.2, 0.2]
world=['green', 'red', 'red', 'green', 'green']
measurements = ['red', 'green']
pHit = 0.6
pMiss = 0.2

def sense(p, Z):
    q=[]
    for i in range(len(p)):
        hit = (Z == world[i])
        q.append(p[i] * (hit * pHit + (1-hit) * pMiss))
    s = sum(q)
    for i in range(len(q)):
        q[i] = q[i] / s
    return q
#
#ADD YOUR CODE HERE
#
p = [sense(p,measurements[i]) for i in range(len(measurements))]

print p
Solution:

INSTRUCTOR NOTE:

Do not modify the sense function. Add code so that p is the correct probability after making the two measurements. Make sure your code works for measurement lists of arbitrary length.

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