Modeling and Multivariate Methods - SAS

474 Clustering Data Chapter 18
Normal Mixtures
Outlier Cluster is used to fit a Uniform cluster to catch any outliers that do not fall into any of the
Normal clusters. If this cluster is created, it is designated cluster 0.
Tours is the number of independent restarts of estimation process, each with different starting values. This
helps to guard against finding local solutions.
Maximum Iterations
algorithm.
is the maximum number of iterations of the convergence stage of the EM
Converge Criteria is the difference in the likelihood at which the EM iterations stop.
For an example of Normal Mixtures, open the Iris.jmp sample data table. This data set was first introduced
by Fisher (1936), and includes four different measurements: sepal length, sepal width, petal length, and
petal width, performed on samples of 50 each for three species of iris.
Note: Your results may not exactly match these results due to the random selection of initial centers.
On the Cluster launch dialog, assign all four variables to the Y, Columns role, select KMeans from Method
menu, and click OK. Select Normal Mixtures from the Method menu, specify 3 for the Number of
Clusters, and click Go. The report is shown in Figure 18.8.
Figure 18.8 Normal Mixtures Report
The report gives summary statistics for each cluster:
• count of number of observations and proportions
• means for each variable
• standard deviations for each variable.
• correlations between variables