SAS/STAT 9.1 Users Guide, Volumes 1-7

Missing Values

An observation with a missing value for the NAME variable is omitted from processing. If the PARENT variable has a missing value but the NAME variable is present, the observation is treated as the root of a tree. A data set can contain several roots and, hence, several trees.

Missing values of the HEIGHT variable are set to upper or lower bounds determined from the nonmissing values under the assumption that the heights are monotonic with respect to the tree structure.

Missing values of the FREQ variable are inferred from nonmissing values where possible; otherwise , they are treated as zero.

Output Data Set

The OUT= data set contains one observation for each leaf in the tree or subtree being processed . The variables are as follows :

• the BY variables, if any

• the ID variable, or the NAME variable if the ID statement is not used

• the COPY variables

• a numeric variable CLUSTER taking values from 1 to c , where c is the number of disjoint clusters. The cluster to which the first observation belongs is given the number 1, the cluster to which the next observation belongs that does not belong to cluster 1 is given the number 2, and so on. ODS Table Names 4757

• a character variable CLUSNAME giving the value of the NAME variable of the cluster to which the observation belongs

The CLUSTER and CLUSNAME variables are missing if the corresponding leaf has a nonpositive frequency.

Displayed Output

The displayed output from the TREE procedure includes the following:

• the names of the objects in the tree

• the height axis

• the tree diagram. A high-resolution graphics tree diagram is produced on the graphics device. The leaves are displayed at the bottom of the graph. Horizontal lines connect the leaves into branches, while the topmost horizontal line indicates the root.

  If the LINEPRINTER option is specified, the root (the cluster containing all the objects) is indicated by a solid line of the character specified by the TREECHAR= option (the default character is ˜X'). At each level of the tree, clusters are shown by unbroken lines of the TREECHAR= symbol with the FILLCHAR= symbol (the default is a blank) separating the clusters. The LEAFCHAR= symbol (the default character is a period) represents singlemember clusters.

By default, the tree diagram is oriented with the height axis vertical and the object names at the top of the diagram. If the HORIZONTAL option is specified, then the height axis is horizontal and the object names are on the left.

ODS Table Names

PROC TREE assigns a name to each table it creates. You can use these names to reference the table when using the Output Delivery System (ODS) to select tables and create output data sets. These names are listed in the following table. For more information on ODS, see Chapter 14, 'Using the Output Delivery System.'