Dirichlet Mean Vector

Problem

For a Dirichlet distribution with concentration vector alphas, return the mean vector with entries alphas[i] / sum(alphas). Return an empty list for an empty vector or any nonpositive concentration.

Hint

Each marginal is a Beta whose mean is the share of total concentration.

Test cases

case 1

in: [[1,1]]

expected: [0.5,0.5]

case 2

in: [[2,3,5]]

expected: [0.2,0.3,0.5]

case 3

in: [[1,1,1,1]]

expected: [0.25,0.25,0.25,0.25]

case 4

in: [[0,1]]

expected: []

case 5

in: [[]]

expected: []

Starter codePython

def dirichlet_mean_vector(alphas):
    # Your code here
    pass

5 test cases · run your code against them in the editor