Chapter 4 Part 2

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Bivariate, Monochrome Symbolization

The visual variables of shape, texture, value and size can be combined to allow monochrome bivariate mapping of linear features. This can be used to present two data sets, or data and meta-data.

Two Nominal Data Sets--Shape and Texture

Figure 4.2a LST.aml Two nominal data sets displayed with shape (primary data) and texture.

This AML (LST.aml) uses two lookup tables to determine symbolization. Because the selection of predefined shape/texture symbols is limited, LINETYPE can be combined with LINETEMPLATE. This is assisted by assigning numeric codes in the shape lookup table:

1000 = WIDE 1001 = DIAMOND 1002 = DOTS 1003 = HASH 1004 = SCALLOP 1005 = SCRUB 1006 = SLANT 1007 = ZIGZAG These codes do not interfere with the Agfa Compugraphic glyph numbers, which this AML will use for LINETYPE MARKER. The second (texture) lookup table requires an integer value that specifies texture (see the texture discussion in Nominal Data--Shape or Texture, above). See Figure 4.2a.

LST <shape_lookup> <texture_lookup> {interval} {size}

<shape_lookup>
specifies either Agfa Compugraphic glyphs or the above codes
<texture_lookup>
specifies an integer code for the LINETEMPLATE
{interval}
a ratio size in PAGEUNITS--the default is 0.1 inches
{size}
specifies a line size--the default is 0.1 inches.


Nominal Data, and Ordinal Data--Shape and Value

Figure 4.2b LSV.aml A nominal data set displayed with shape and an ordinal data set displayed with value. This is more effective with meta-data than a second data set.

Shape should be used to specify nominal differences and value should be used to specify ordinal differences. Generally, value should be used for meta-data and size (the next AML) should be used for a second data set. This AML (LSV.aml) requires a lookup table that relates nominal distinctions to line symbols in a lineset, and a second lookup table that specifies HLS values. See Figure 4.2b.

LSV <shape_lookup> <value_lookup> {lineset} {linesize} {hue} {intensity}

<shape_lookup>
specifies line symbol numbers
<value_lookup>
specifies HLS lightness data (from 0 to 80)
{lineset}
specifies a lineset for shapes--defaults to the current lineset
{linesize}
specifies a line width--defaults to 0.1 inches
{hue} {intensity}
specify a color that will be value shaded.


Nominal Data, and Ratio Data--Shape and Size

Figure 4.2c LSZ.aml A nominal data set displayed with texture and a ratio data set displayed with size. Size is more effective than value in conveying a second data set.

The AML, LSZ.aml, should be used for two data sets--one of nominal information (shape or texture) and one of ordinal to ratio information (size). Like the shape and value AML, this AML requires a lookup table that relates nominal categories to line symbols, but requires the specification of a ratio data item in the line coverage's attribute table. See the discussion of size specification on page 50 and Figure 4.2d.

LSZ <shape_lookup> <size_item> {lineset} {scale_factor} {size_factor} {minimum_size}

<shape_lookup>
specifies line symbol numbers
<size_item>
an ratio data item in the attribute table referenced by <shape_lookup>
{lineset}
specifies a lineset for shapes--defaults to the current lineset
{size_exponent} {size_factor} {minimum_size}
define the scaling of sizes,
defaults: size_exponent = 1; size_factor = 0.15; minimum_size = 0.02 inches.


Ratio Data, and Ordinal Data--Size and Value

Figure 4.2d LVZ.aml Ratio data displayed with size, which is value shaded on the basis of meta-data.

This AML uses size to indicate a ratio data set, and value to represent a second data set. Because of the establishment of visual levels by both size and value, this combination is good for conveying data and meta-data. The AML requires a numeric attribute item for size, and a lookup table for HLS value specification. See Figure 4.2d and LVZ.aml.

LVZ <value_lookup> <size_item> {size_exponent} {size_factor} {minimum_size} {hue} {intensity}

<value_lookup>
specifies HLS lightness data (from 0 to 80)
<size_item>
a ratio data item in the attribute table referenced by <value_lookup>
{size_exponent} {size_factor} {minimum_size}
define the scaling of sizes,
defaults: size_exponent = 1; size_factor = 0.15; minimum_size = 0.02 inches
{hue} {intensity}
specify a color that will be value shaded.



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