Algorithms

The CLUSTER Procedure

Algorithms

Anderberg (1973) describes three algorithms for implementing agglomerative hierarchical clustering: stored data, stored distance, and sorted distance. The algorithms used by PROC CLUSTER for each method are indicated in Table 23.2. For METHOD=AVERAGE, METHOD=CENTROID, or METHOD=WARD, either the stored data or the stored distance algorithm can be used. For these methods, if the data are distances or if you specify the NOSQUARE option, the stored distance algorithm is used; otherwise, the stored data algorithm is used.

Table 23.2: Three Algorithms for Implementing Agglomerative Hierarchical Clustering

	Algorithm
Stored	Stored	Stored	Sorted
Method	Data	Distance	Distance
AVERAGE	x	x
CENTROID	x	x
COMPLETE		x
DENSITY			x
EML	x
FLEXIBLE		x
MCQUITTY		x
MEDIAN		x
SINGLE		x
TWOSTAGE			x
WARD	x	x

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