Feature Space (Nearest Neighbor Analysis)
The feature space chart is an interactive graph of the feature space (or a subspace, if there are more than 3 features). Each axis represents a feature in the model, and the location of points in the chart show the values of these features for cases in the training and holdout partitions.
Keys. In addition to the feature values, points in the plot convey other information.
- Shape indicates the partition to which a point belongs, either Training or Holdout.
- The color/shading of a point indicates the value of the target for that case; with distinct color values equal to the categories of a categorical target, and shades indicating the range of values of a continuous target. The indicated value for the training partition is the observed value; for the holdout partition, it is the predicted value. If no target is specified, this key is not shown.
- Heavier outlines indicate a case is focal. Focal cases are shown linked to their k nearest neighbors.
Controls and Interactivity. A number of controls in the chart allow you explore the Feature Space.
- You can choose which subset of features to show in the chart and change which features are represented on the dimensions.
- “Focal cases” are simply points selected in the Feature Space chart. If you specified a focal case variable, the points representing the focal cases will initially be selected. However, any point can temporarily become a focal case if you select it. The “usual” controls for point selection apply; clicking on a point selects that point and deselects all others; Control-clicking on a point adds it to the set of selected points. Linked views, such as the Peers Chart, will automatically update based upon the cases selected in the Feature Space.
- You can change the number of nearest neighbors (k) to display for focal cases.
- Hovering over a point in the chart displays a tooltip with the value of the case label, or case number if case labels are not defined, and the observed and predicted target values.
- A “Reset” button allows you to return the Feature Space to its original state.