Attributes Attribute Data Row 1 entity Column 1

Attributes

Attribute Data • Row = 1 entity • Column = 1 attribute N M LU O C • Record non-spatial characteristics that describe spatial entity • Arranged in tables ROW • Stored in a computer in a flat-file format or a Database Management System (DBMS)

Attributes Position Color Service Date Flow

Attribute Categories • Nominal Attributes • Provide descriptive information • Ex: color, city name, plant type • No implied order, size, or other quantitative info • May also be images, movies, sounds

Attribute Categories • Ordinal Attributes • Imply a ranking or order by their values • Use descriptive or numerical attributes • Ex: High/Medium/Low or 100/50/1 • Specifies rank only, does not specify scale • Ex: High/50 is ordered higher than Low/1, but we do not know by how much

Attribute Categories • Interval • Rank order and magnitude is implied. • Does not have a natural zero. • Uses an arbitrary zero point instead. • Use numerical attributes. • Ex: 50°F is 10°F more than 40°F • Addition and subtraction make sense, but not multiplication since values are relative from an arbitrary zero.

Attribute Categories • Ratio • Rank order and magnitude is implied. • Has a natural zero. • Use numerical attributes. • Ex: 50 MPH is twice as fast and greater than 25 MPH • Addition, subtraction, multiplication, and division make sense, as the values are absolute from a natural zero.

1 3 4 2 Identify Columns as: Nominal Ordinal Interval/Ratio ID Height(ft) Type Class 1 15 Pine Medium 2 20 Pine Medium 3 8 Mesquite Small 4 30 Oak Tall

Attribute Data Types • Attributes are stored in computer memory. • The data type of the attribute needs to be specified for efficient use of memory and determination of operation applicability. • There are four typical data types • • Integer Float/Real Text/String Date

Attribute Data Types • Integer • E. g. whole number • Can be used for mathematical calculations • However, any resulting fraction of a whole number will be rounded • Examples: • 1 • 2458 • -54

Attribute Data Types • Float/Real • E. g. decimal number • Can be used for mathematical calculations • Examples: • 1. 452 • 254783. 1 • -845. 157

Attribute Data Types • Text/String • • E. g. characters Cannot be used for mathematical calculations Strings can be manipulated, however. e. x. Extract substring Examples: • • “a” “GIS” “ 125 Main St. ” “ 9”

Attribute Data Types • Date • • Holds date information Cannot be used for mathematical calculations Lengths of time can be calculated, however Examples: • 12/10/2010 • 10/12/10 • December 10 2010