Glossary for Geospatial Science

categorical data:  Data in a raster object is said to be categorical if it cannot be represented by a continuous surface, since intermediate terms cannot be derived with meaningful results.  Example 1: soil type data cannot be interpolated, since a soil type 14 and a soil type 15 cannot sensibly be averaged to derive a soil type 14.5.  Example 2: feature classification data cannot be interpolated, since a cell assigned membership in the feature “corn” cannot sensibly be used in any process that averages it with a cell assigned membership in the feature “wheat.”

Do not confuse the terms “categorical data” and “category”—they have different and distinct meanings.