Geographic Information Systems: An Introduction, 3rd Edition

14.8 Complex Operations of Attribute Data

Mathematical, logical, and statistical operations may be performed on attribute data (Figures 14.8 to 14.11). The mathematical operations include addition, subtraction, multiplication, division, exponential, square root, and the trigonometric functions:

The logical operations require the operators of set algebra: equal to, greater than, and less than, and combinations thereof:

=, >, <, ≥, ≤, < >

as well as those of Boolean algebra:

AND, OR, NOR, and NOT

The statistical operations include sum, maxima, minima, average, weighted average, frequency distribution, bidirectional comparison, standard deviation, multivariate, and others.

Attribute data may be either quantitative and expressed numerically, or qualitative without numerical magnitudes. Numerical operations may be performed only on numerical data and hence mainly on quantitative attribute data. The numerical treatment of qualitative attribute data is limited to counting operations, as in determining the number of classes into which data may be ranked or how many observations fall within each class. For example, four classes—A, B, C, and D—may be identified and found to contain differing numbers of observations: 12 in A, 23 in B, 2 in C, and 9 in D. Attribute data are frequently processed to discern new patterns and relations in the data.

Figure 14.8

Arithmetic operation on attribute ...