How to write a confusion matrix in Python?

Question

I wrote a confusion matrix calculation code in Python:

def conf_mat(prob_arr, input_arr):
        # confusion matrix
        conf_arr = [[0, 0], [0, 0]]

            


        

Answer 1

You should map from classes to a row in your confusion matrix.

Here the mapping is trivial:

def row_of_class(classe):
    return {1: 0, 2: 1}[classe]

In your loop, compute expected_row, correct_row, and increment conf_arr[expected_row][correct_row]. You'll even have less code than what you started with.