QQ Plot Slope and Intercept

Problem

Fit a line through the points (theoretical quantile, sample quantile) using population moments and return [slope, intercept], where slope = cov(q, s)/var(q) and intercept = mean(s) - slope*mean(q). Return [0.0, 0.0] when fewer than two points are given or the theoretical quantiles are constant.

Hint

It is ordinary least squares on the quantile pairs.

Test cases

case 1

in: [[-1,0,1],[2,4,6]]

expected: [2,4]

case 2

in: [[0,1,2],[1,3,5]]

expected: [2,1]

case 3

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

expected: [0,3]

case 4

in: [[5,5],[1,2]]

expected: [0,0]

case 5

in: [[1],[1]]

expected: [0,0]

Starter codePython

def qq_slope_intercept(theoretical, sample):
    # Your code here
    pass

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