聚类 Dunn Index 度量指标的数学公式与 Python 源码

数学公式见：

https://www.orzzz.net/directory/mathematics/MultivariateStatisticalAnalysis/CrispClusterValidityIndices/index.html

Python 代码：

def DunnIndex(C: list[list[list]]) -> float:
    Euclidean = lambda a, b: sum([abs(i - j) ** 2 for i, j in zip(a, b)]) ** (1 / 2)
    return min(
        min(Euclidean(cs, ct) for cs in Ci for ct in Cj)
        for i, Ci in enumerate(C) for j, Cj in enumerate(C) if i < j
    ) / max(
        max(Euclidean(cs, ct) for cs in Ci for ct in Ci)
        for Ci in C
    )

if __name__ == '__main__':
    C = [
        [[5.1, 3.5, 1.4, 0.2],
         [4.9, 3.0, 1.4, 0.2],
         [5.0, 3.3, 1.4, 0.2]],

        [[4.9, 2.4, 3.3, 1.0],
         [6.6, 2.9, 4.6, 1.3]],

        [[6.5, 3.0, 5.5, 1.8],
         [7.7, 3.8, 6.7, 2.2],
         [7.2, 3.2, 6.0, 1.8],
         [6.4, 2.8, 5.6, 2.1]]
    ]
    print(DunnIndex(C))