Partition Plot

Each point in the Partition Plot represents an observation in the data table. If validation is used, the plot shows only observations in the training data. The initial partition plot does not show splits. The appearance of the Partition plot is different for continuous and categorical responses.

Partition Plot for a Continuous Response

If the response is continuous, the left vertical axis represents the values of the observations. There is an initial horizontal line on the plot that is the overall mean of the response. Once you begin splitting, additional horizontal lines are added that show the mean response value for each node of the decision tree. Splits are shown below the horizontal axis with a text description and a vertical line. Observations are reorganized into their respective nodes as splits are created or removed. The most recent split appears directly below the horizontal axis and on top of existing splits. The plot is updated with each split or prune of the decision tree.

Figure 4.6 Partition Report for a Continuous Response 

Partition Plot for a Categorical Response

If the response is categorical, the left vertical axis represents the proportion of each response outcome and the right vertical axis shows the order in which the response levels are plotted. There is an initial horizontal line on the plot that is the overall proportion of the first plotted response level. Once you begin splitting, additional horizontal lines are added that show the proportion of the first plotted response level for each node of the decision tree. Splits are shown below the horizontal axis with a text description and a vertical line that splits the observations in the plot. The vertical lines extend into the plot and indicate the boundaries for each node. The most recent split appears directly below the horizontal axis and on top of existing splits. The plot is updated with each split or prune of the decision tree.

Figure 4.7 Partition Report for a Categorical Response