CAGE User's Guide

Filling the Table by Extrapolation

Filling a table by extrapolation fills the table with values based on the values already placed in the extrapolation mask. The extrapolation mask is described below.

To fill a table by extrapolating over a preselected mask, click  or select Table -> Extrapolate.

This extrapolation does one of the following:

• If the extrapolation mask has only one value, all the cell values change to the value of the cell in the mask.
• If the extrapolation mask has two or more collinear values, the cell values change to create a plane parallel to the line of values in the mask.
• If the extrapolation mask has three or more coplanar values, the cell values change to create that plane.
• If the extrapolation mask has four or more ordered cells (in a grid), the extrapolation routine fills the cells by a grid extrapolation.
• If the extrapolation mask has four or more unordered (scattered) cells, the extrapolation routine fills the cell values using a thin plate spline interpolant (a type of radial basis function).

Using the Extrapolation Mask

The extrapolation mask defines a set of cells that form the basis of any extrapolation.

For example, a speed-load (or relative air-charge) table has values in the following ranges that you consider to be accurate:

• Speed 3000 to 5000 rpm
• Load 0.4 to 0.6

You can define an extrapolation mask to include all the cells in these ranges. You can then fill the rest of your table based on these values.

To add or remove a cell from the extrapolation mask:

1. Right-click the table
2. Select Add to/Remove from Mask from the menu.

Cells included in the extrapolation mask are colored yellow.

Cells that are locked and in the extrapolation mask are colored green.

Generating the Extrapolation Mask from the Predicted Error

Predicted error (PE) is the standard deviation of the error between the model and the data used to create the model. You can automatically generate an extrapolation mask based on the predicted error.

To generate a mask automatically:

1. Right-click the Menu button of the table and select Generate Extrapolation Mask from Predicted Error.
2. In the dialog box, set the PE threshold. Click OK.

The cells in the table where the predicted error is within the threshold now form the extrapolation mask, and thus are colored yellow.

Optimizing Table Values

Inverting a Table