• Introduction
• The Utility of Maps
• Producing Displays
• Point Symbolization
• Line Symbolization
• Choropleth Symbolization
• Graduated Symbol
• Grid Symbolization
• Dot Density Symbolization
  • Monovariate
  • Bivariate Monochrome
  • Bivariate Color
  • Multivariate
• Isopleth Symbolization
• Thematic Mapping
• References
• Index
• Author Index
• Symbol Index
• Site Map

Monochrome, Bivariate Symbolization

Monochrome bivariate maps are limited to dot density texture and color value. This can be used to display two data values, or data (texture) and meta-data (value).

Ratio Data, and Ordinal Data--Texture and Value

Figure 8.1c: DDV.aml Ratio data displayed with dot density texture and ordinal data displayed with color value. This can be used to show ratio meta-data.

Dot density maps that show more than texture must use a dot size larger than that needed for texture alone. This is because specification of halftone shades (such as those used by printers) requires more than one pixel (which can only be on or off). The macro, DDV.aml, adjusts for this by using a larger dot size. See Figure 8.1c.

DDV <dot_lookup> <value_lookup> {dot_size} {hue} {intensity}

<dot_lookup>

specifies dot density in hundredths of PAGEUNITS

<value_lookup>

specifies HLS lightness (from 10 to 100)

{dot_size}

the size of a dot--defaults to 0.03 inches

{hue} {intensity}

specify a color to be value shaded.

Bivariate Dot Density Legends

Figure 8.1d: DDBL.aml A legend for figure 8.1c. This AML can also be used to generate a legend for dot density and hue maps.

Like single variable legends, bivariate legends must convey the idea of continuity in dot density, as well as display the character of the second variable. The macro will display hue (nominal) data in separate rows, and value (ordinal) data as continuous. See DDBL.aml and Figure 8.1d.

DDBL <dot_lookup> <lookup_2> <start_x> <start_y> <size_x> <size_y> <h|v> {dot_size} {textset} {font} {text_size} {float_precision} {color_parameter_1} {color_parameter_2}

<dot_lookup>

the lookup table used to specify dot density

<lookup_2>

the lookup used to specify hue or value

<start_x> <start_y>

the lower left corner of the legend box

<size_x> <size_y>

the size of the legend box

<h|v>

Hue or Value symbolization

{dot_size}

the size of dot used in the map--defaults to 0.03 inches

{textset} {font} {text_size}

define the labelling text--defaults to a 10 point roman font

{float_precision}

the number of decimal places shown--defaults to 2

{color_parameter_1}

for Hue, value; for Value, hue

{color_parameter_2}

intensity--defaults are the same as the mapping AMLs.