6.9.9. Adding and populating a new field in attribute table

Now, to obtain a value for all of the other land cover classes besides 211, 312, and 313, we will create a new column in the table and then calculate the values of “other” land cover values inside each buffer.

  1. Open the Table Options for the colony_locations layer.
  2. Click Add Field.
  3. Name: LC_other.
  4. Choose the Type Float.
  5. Use the field calculator to populate this column. Right-click on LC_other field name.
  6. Select Field calculator. Fill out the dialog box according to Fig. 57 with the equation: 1 - ([stats211:MEAN] + [stats312:MEAN] + [stats313:MEAN]) which calculates the percentage of “other” land cover types in relation to the three we have already used.
  7. You will end up with a table similar to the one in Fig. 58. We will use these four new fields later in the Map creation section (6.10.).

Note: as you can see in Fig. 58, there are “<NULL>” values for FID 16. This seems to be a glitch in the Zonal Statistics as Table tool. There are ways this can be fixed in the table but we will not deal with them now.

Fig. 57. The Field Calculator dialog box used to create the “other” landcover classification in the colony locations table.


Fig. 58.
The resulting colony locations attribute table with land covers means.