A simple example of computation is to create a new attribute called feet for a trail map that is mea- sured in meters. This new attribute can be computed by"length" x 3.28, where length is an existing at tribute. Another example is to create a new attribute that measures the quality of wildlife habitat by eval uating the existing attributes of slope, aspect, and el- g evation. The task first requires a scoring system for each variable. Once the scoring system is in place, a we can compute the index value for measuring the u quality of wildlife habitat by summing the scores of n slope, aspect, and elevation. In some cases, differ- n ent weights may be assigned to different variables. For example, if elevation is three times as important 0 as slope and aspect, then we can compute the index value by using the following equation: slope score aspect score 3 x elevation score. Chapter 8 w has a section on index models.