Created
March 19, 2023 12:30
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Theil's U & Cramer's V
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| def cramers_v(x, y): | |
| confusion_matrix = pd.crosstab(x,y) | |
| chi2 = ss.chi2_contingency(confusion_matrix)[0] | |
| n = confusion_matrix.sum().sum() | |
| phi2 = chi2/n | |
| r,k = confusion_matrix.shape | |
| phi2corr = max(0, phi2-((k-1)*(r-1))/(n-1)) | |
| rcorr = r-((r-1)**2)/(n-1) | |
| kcorr = k-((k-1)**2)/(n-1) | |
| return np.sqrt(phi2corr/min((kcorr-1),(rcorr-1))) | |
| def conditional_entropy(x,y): | |
| # entropy of x given y | |
| y_counter = Counter(y) | |
| xy_counter = Counter(list(zip(x,y))) | |
| total_occurrences = sum(y_counter.values()) | |
| entropy = 0 | |
| for xy in xy_counter.keys(): | |
| p_xy = xy_counter[xy] / total_occurrences | |
| p_y = y_counter[xy[1]] / total_occurrences | |
| entropy += p_xy * math.log(p_y/p_xy) | |
| return entropy | |
| def theils_u(x, y): | |
| s_xy = conditional_entropy(x,y) | |
| x_counter = Counter(x) | |
| total_occurrences = sum(x_counter.values()) | |
| p_x = list(map(lambda n: n/total_occurrences, x_counter.values())) | |
| s_x = ss.entropy(p_x) | |
| if s_x == 0: | |
| return 1 | |
| else: | |
| return (s_x - s_xy) / s_x |
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