K-means

組內變異

$$\begin{aligned} \operatorname{W}(C_k)&:=\frac{1}{|C_k|}\sum_{i,i'\in{C_k}}\operatorname{D_{Euclidean}^2}(x_i,x_{i'}) \\ &=\frac{1}{n_{c_k}}\sum_{i,i'\in{C_k}}\sum_{j=1}^p(x_{i,j}-x_{i',j})^2 \\ &=2\times\sum_{i}^N\sum_{j=1}^p(x_{i,j}-\bar{x}_{k,j})^2 \end{aligned}$$

Hierarchical Clustering

依照下列方式計算Linkage，並逐個依據當前最小的Linkage合併兩Cluster