Interpreting average linkage clustering results in SPSS I am trying to cluster 6 PC scores for a 1600 cases data (so its a 1600 x 6 matrix). I am using average linkage clustering technique that would be followed by a K mean clustering. The purpose of Average linkage clustering is to provide seed values for K mean clustering.
Would somebody explain me how to extract the results of average linkage clustering from Agglomeration Schedule?
 A: You need not to use agglomeration schedule for your task. You need to (1) decide how many clusters are there, (2) save this cluster solution as cluster membership variable, (3) compute centres - vector of means, for each cluster, (4) input it into K-MEANS clustering as "initial centres".
Perhaps you ought to do (2) first (save range of solutions) and (1) then (decide upon the "best" solution with the advise of some clustering criterion or other approach).
Note, however, that 1600 cases is too much for hierarchical clustering - not just because of computer-performance issues, but because hierarchical clustering is one-path greedy algorithm and therefore is prone to produce suboptimal results on distant steps of agglomeration.
A: You don't say why you chose the average linkage method, but since you are only doing that step to generate starting values for k means, the choice of method in the first step might not be very important.  Ward's method, also available in the SPSS CLUSTER procedure, may scale better to larger datasets.  If the dataset for the first stage turns out to be too large, you could take a random sample to calculate the initial cluster centers.
HTH,
Jon Peck
