User manual SPSS CLASSIFICATION TREES 13.0

[. . . ] SPSS Classification Trees 13. 0 TM For more information about SPSS® software products, please visit our Web site at http://www. spss. com or contact SPSS Inc. 233 South Wacker Drive, 11th Floor Chicago, IL 60606-6412 Tel: (312) 651-3000 Fax: (312) 651-3668 SPSS is a registered trademark and the other product names are the trademarks of SPSS Inc. No material describing such software may be produced or distributed without the written permission of the owners of the trademark and license rights in the software and the copyrights in the published materials. Use, duplication, or disclosure by the Government is subject to restrictions as set forth in subdivision (c) (1) (ii) of The Rights in Technical Data and Computer Software clause at 52. 227-7013. [. . . ] If you have specified multiple target categories, a separate set of rules is generated for each target category. Note 2: For SPSS and SQL rules for selecting cases (not rules for assigning values), All nodes and All terminal nodes will effectively generate a rule that selects all cases used in the analysis. Export rules to a file. Saves the rules in an external text file. You can also generate and save selection or scoring rules interactively, based on selected nodes in the final tree model. For more information, see "Case Selection and Scoring Rules" in Chapter 2 on p. Note: If you apply rules in the form of SPSS command syntax to another data file, that data file must contain variables with the same names as the independent variables included in the final model, measured in the same metric, with the same user-defined missing values (if any). Chapter Tree Editor 2 With the Tree Editor, you can: Hide and show selected tree branches. Control display of node content, statistics displayed at node splits, and other information. Create and save rules for selecting or scoring cases based on selected nodes. To edit a tree model: E Double-click the tree model in the Viewer window. or E Right-click the tree model in the Viewer window, and from the context menu choose: SPSS Tree Object Open Hiding and Showing Nodes To hide (collapse) all the child nodes in a branch beneath a parent node: E Click the minus sign (­) in the small box below the lower right corner of the parent node. All nodes beneath the parent node on that branch will be hidden. 49 50 Chapter 2 To show (expand) the child nodes in a branch beneath a parent node: E Click the plus sign (+) in the small box below the lower right corner of the parent node. Note: Hiding the child nodes on a branch is not the same as pruning a tree. If you want a pruned tree, you must request pruning before you create the tree, and pruned branches are not included in the final tree. For more information, see "Pruning Trees" in Chapter 1 on p. 17. Figure 2-1 Expanded and collapsed tree Selecting Multiple Nodes You can select cases, generate scoring and selections rules, and perform other actions based on the currently selected node(s). E Ctrl-click the other nodes you want to select. 51 Tree Editor You can multiple-select sibling nodes and/or parent nodes in one branch and child nodes in another branch. You cannot, however, use multiple selection on a parent node and a child/descendant of the same node branch. Working with Large Trees Tree models may sometimes contain so many nodes and branches that it is difficult or impossible to view the entire tree at full size. There are a number of features that you may find useful when working with large trees: Tree map. You can use the tree map, a much smaller, simplified version of the tree, to navigate the tree and select nodes. You can zoom out and zoom in by changing the scale percentage for the tree display. You can make a tree more compact by displaying only tables or only charts in the nodes and/or suppressing the display of node labels or independent variable information. For more information, see "Controlling Information Displayed in the Tree" on p. 55. Tree Map The tree map provides a compact, simplified view of the tree that you can use to navigate the tree and select nodes. To use the tree map window: E From the Tree Editor menus choose: View Tree Map 52 Chapter 2 Figure 2-2 Tree map window The currently selected node is highlighted in both the Tree Model Editor and the tree map window. The portion of the tree that is currently in the Tree Model Editor view area is indicated with a red rectangle in the tree map. [. . . ] The correct classification rate for good credit cases, however, has declined from 82. 8% with CHAID to 74. 8% with CRT. 121 Missing Values in Tree Models Surrogates The differences between the CHAID and CRT models are due, in part, to the use of surrogates in the CRT model. The surrogates table indicates how surrogates were used in the model. Figure 6-10 Surrogates table At the root node (node 0), the best independent (predictor) variable is number of credit cards. For any cases with missing values for number of credit cards, car loans is used as the surrogate predictor, since this variable has a fairly high association (0. 643) with number of credit cards. If a case also has a missing value for car loans, then age is used as the surrogate (although it has a fairly low association value of only 0. 004). [. . . ]