Mean-Center by User

Problem

Center each user's ratings by their observed mean.

For every row, compute the mean over nonzero entries only, subtract it from those entries, and leave zeros as 0.0. A row with no ratings stays all zeros.

Hint

Users rate on different scales; centering removes each user's personal bias.

Test cases

case 1

in: [[[5,0,3],[0,0,0]]]

expected: [[1,0,-1],[0,0,0]]

case 2

in: [[[2,4],[6,2]]]

expected: [[-1,1],[2,-2]]

case 3

in: [[[1,2,3]]]

expected: [[-1,0,1]]

case 4

in: [[[0,0],[80,20]]]

expected: [[0,0],[30,-30]]

Starter codePython

def mean_center_by_user(matrix):
    # Your code here
    pass

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