11.2 Viewing Split Data Histograms

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11.2.1 Creating Histograms

[Picture]
Figure 11.1: The node’s submenu showing the Histogram highlighted for display.

A histogram works on any node. If the node is a leaf node (cannot be further split), or is the parent of a regression, you will see a single histogram. If the node has two or more child nodes, you will see a histogram for each parent and child node and you can see their relationship. In Fig: 11.1 we have a parent and three child nodes.

Using the pop up menus that shows up by clicking on the parent node, choose Visualize Split Data->Histogram.

11.2.2 Visualizing Node Relationships

[Picture]
Figure 11.2: A view of a histogram with the top child node’s graph selected.

The top histogram represents the parent node and the bottom three the children. By clicking on the histogram of the top child node, the graph changes color and overlays its histogram on the parent node in the same color.

Vertical lines for the mean (μ) and the median (50%) are drawn on each histogram.

11.2.3 Changing Bins

[Picture]
Figure 11.3: A view of the histogram after the slider has been moved to show fewer bins for the data.

There is a slider control at the bottom right of the dialog for changing the number of bins. This controls how many bars or bins represent the data. If you want more detail, increase the number of bins. Clicking the Reset View button resets the histograms to their original, default view. The slider incrementally changes by a power of two.

11.2.4 Zooming or Rubber Banding Data

[Picture]
Figure 11.4: The rectangular area of the first child node is delineated for zooming-in.

You can zoom-in on a particular area of the data by right clicking and holding down the right mouse right button and dragging diagonally across the histogram to create a rectangle over an interesting area of a histogram (like stretching a rubberband). The selected area expands to the length of the full histogram.

Zooming the parent histogram zooms all of the child histograms. Zooming a child histogram only zooms that child.

[Picture]
Figure 11.5: The resultant zoom-in from the area delineated on the first child histogram in Fig. 11.4.

The Undo Rubberband button undoes the zooming effect. Sequential zoom requests of various regions of the histogram can be undone by clicking this button once for every zoom. A history of the last 5 most recent zoom requests is available.

11.2.5 Menus

Here is what the simple menus structures do:


Menu Selections Does This
File->Bitmap Allow you to save a BMP file as an image of the histogram(s).
File->Print Lets you print the histogram(s).
File->Close Closes the histogram view.
Help->Help Opens a simple help screen.

11.2.6 File->Print

[Picture]
Figure 11.6: The histogram per page dialog window

From the File menu, selecting Print will bring up a dialog from which you can select how many histograms you would like printed per page.

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