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The GMAP Procedure

PRISM Statement

Creates three-dimensional prism maps in which levels of magnitude of the specified response variables are represented by polyhedrons (raised polygons) of varying height, pattern, and color.

Requirements: At least one response variable is required. You must use the ID statement in conjunction with the PRISM statement.
Global statements: FOOTNOTE, LEGEND, PATTERN, TITLE

Description

The PRISM statement specifies the variable or variables that contain the data that are represented on the map by raised map areas. This statement automatically

You can use statement options to control the ranges of the response values, specify the angle of view, and enhance the appearance of the map.

In addition, you can use global statements to modify the map area patterns and the legend, as well as add titles and footnotes to the map. You can also use an Annotate data set to enhance the map.

For maps that contain intersecting polygons or polygons within polygons, extremely complicated maps, or maps that contain line segments that cross, use the GREDUCE procedure to reduce and simplify the map if necessary.
PRISM response-variable(s) </ option(s)>;

option(s) can be one or more options from any or all of the following categories:

Required Arguments

response-variable(s)
specifies one or more variables in the response data set that contains response values represented on the map. Each response variable produces a separate map. All variables must be in the input data set. Separate multiple response variables with blanks.

Missing values for the response variable are not considered valid unless you use the MISSING option in the PRISM statement.

Response variables can be either numeric or character. Numeric response variables with continuous values are grouped into ranges, or response levels. Each response level is assigned a different prism height and a different pattern and color combination. Character variables and numeric variables (when you use the DISCRETE option) have a different response level for each unique response variable value. This means that the prism height can be used to identify discrete values, but prism height does not reflect the specific value. Use the legend to determine the exact value of a discrete variable. Numeric variables are treated as continuous unless you use DISCRETE.

For numeric response variables with continuous values, you can control the selection of response level ranges using the MIDPOINTS= or LEVELS= option. By default, the GMAP procedure determines the number of levels for the map using the formula FLOOR(1+3.3 log(N)), where N is the number of unique map area identification variable values.
See also: About Response Variables

Options

Options in a PRISM statement affect all graphs that are produced by that statement. You can specify as many options as you want and list them in any order.

ANNOTATE=Annotate-data-set
ANNO=Annotate-data-set
specifies a data set to annotate maps that are produced by the PRISM statement.

Note:   Annotate coordinate systems 1, 2, 7, and 8 are not valid with prism maps.  [cautionend]
See also: The Annotate Data Set

CEMPTY=empty-area-outline-color
outlines empty map areas in the specified color. This option affects the map areas that are empty. Empty map areas are generated in prism maps either

The default outline color is the same as the default COUTLINE= color.
See also: ALL and Displaying Map Areas and Response Data

COUTLINE=nonempty-area-outline-color | SAME
outlines non-empty map areas in the specified color. SAME specifies that the outline color of a map area is the same as the interior pattern color.

The default outline color depends on the PATTERN statement:

Note:   If you specify empty map patterns, (VALUE=MEMPTY in a PATTERN statement) you should not change the outline color from the default value, SAME, to a single color. Otherwise all the outlines will be one color and you will not be able to distinguish between the empty areas.  [cautionend]
Featured in: Producing a Simple Prism Map

CTEXT=text-color
specifies a color for the text in the legend. If you omit the CTEXT= option, a color specification is searched for in this order:

  1. the CTEXT= option in a GOPTIONS statement

  2. the default, the first color in the colors list.

The CTEXT= color specification is overridden if you also use the COLOR= suboption of a LABEL= or VALUE= option in a LEGEND definition assigned to the map legend. The COLOR= suboption determines the color of the legend label or the color of the legend value descriptions, respectively.

DESCRIPTION='entry-description'
DES='entry-description'
specifies the description of the catalog entry for the chart. The maximum length for entry-description is 40 characters. The description does not appear on the chart. By default, the GMAP procedure assigns a description of the form PRISM MAP OF variable, where variable is the name of the map variable.

DISCRETE
treats a numeric response variable as a discrete variable rather than as a continuous variable. The DISCRETE option does not group the response values into ranges; instead, the GMAP procedure uses a separate response level (prism height, color, and surface pattern) for each different value of the formatted response variable. The LEVELS= option is ignored when you use the DISCRETE option.

Use this option if your numeric response variable is assigned a user-written format.

Note:   If the data do not contain a value in a particular range of the format, that formatted range is not displayed in the legend.  [cautionend]
Featured in: Creating Maps with Drill-down for the Web (with CHORO statement)

HTML=variable
identifies the variable in the input data set whose values create links in the HTML file created by the ODS HTML statement. These links are associated with an area of the chart and point to the data or graph you wish to display when the user drills down on the area.

HTML_LEGEND=variable
identifies the variable in the input data set whose values create links in the HTML file created by the ODS HTML statement. These links are associated with a legend value and point to the data or graph you wish to display when the user drills down on the value.

LEGEND=LEGEND<1...99>
assigns the specified LEGEND definition to the map legend. LEGEND= is ignored if the specified LEGEND definition is not currently in effect. In the GMAP procedure, the PRISM statement produces a legend unless you use the NOLEGEND option. If you use the SHAPE= option in a LEGEND statement, only the value BAR is valid.
See also: LEGEND Statement
Featured in: Specifying Midpoints in a Prism Map

LEVELS=number-of-response-levels
specifies the number of response levels to be graphed when the response variables are continuous. Each level is assigned a different prism height, surface pattern, and color combination.

If neither the LEVELS= option nor the DISCRETE option is used, the GMAP procedure determines the number of response levels that use the formula FLOOR(1+3.3 log(N)), where N is the number of unique map area identification variable values.

The LEVELS= option is ignored when you use the DISCRETE or MIDPOINTS= option.
Featured in: Specifying Response Levels in a Block Map

MIDPOINTS=value-list
specifies the response levels for the range of response values that are represented by each level (prism height, pattern, and color combination).

For numeric response variables, value-list is either an explicit list of values, or a starting and an ending value with an interval increment, or an combination of both forms:
n <...n>
n TO n <BY increment>
n <...n> TO n <BY increment > <n <...n> >

By default the increment value is 1. You can specify discrete numeric values in any order. In all forms, n can be separated by blanks or commas. For example, 

midpoints=(2 4 6)
midpoints=(2,4,6)
midpoints=(2 to 10 by 2)

If a numeric variable has an associated format, the specified values must be the unformatted values.

For character response variables, value-list has this form:
'value-1' <...'value-n'>

The values are character strings enclosed in single quotation marks and separated by blanks. For example, 

midpoints='Midwest' 'Northeast' 'Northwest'

Specify the values in any order. If a character variable has an associated format, the specified values must be the formatted values.

You can selectively exclude some response variable values from the map, as shown here: 

midpoints='Midwest'

Only those observations for which the response variable exactly matches one of the values listed in the MIDPOINTS= option are shown on the map. As a result, observations may be inadvertently excluded if values in the list are misspelled or if the case does not match exactly.
Featured in: Specifying Midpoints in a Prism Map

MISSING
accepts a missing value as a valid level for the response variable.
See also: Displaying Map Areas and Response Data

NAME='entry-name'
specifies the name of the catalog entry for the map. The maximum length for entry-name is eight characters. The default name is GMAP. If that name that you specify duplicates the name of an existing entry, SAS/GRAPH software adds a number to the duplicate name to create a unique entry, for example, GMAP1.

NOLEGEND
suppresses the legend.

XLIGHT=x
YLIGHT=y
specify the coordinates of the imagined light source in the map coordinate system. The position of the light source affects the way the sides of the map polygons are shaded. Although you can specify any point for the light source using the XLIGHT= and YLIGHT= options, the light source is actually placed in one of only four positions.

Light Source Coordinates shows how the point you specify is positioned.

Light Source Coordinates
Specified Light Source Light Source Position
in quadrants I or II, or on the X or +Y axis behind the map (point A), and all side polygons are shadowed
on or within approximately 10 degrees of the Y axis the viewing position (point D), and none of the side polygons are shadowed
in quadrant III (except within 10 degrees of the Y axis) to the left of the map (point B), and the right-facing sides of polygons are shadowed
in quadrant IV (except within 10 degrees of the Y axis) to the right of the map (point C), and the left-facing side polygons are shadowed

Coordinates of Imagined Light Source in a Map Coordinate System illustrates the light source positions. Assume that your viewing position, selected by the XVIEW=, YVIEW=, and ZVIEW= options, is point D.

Coordinates of Imagined Light Source in a Map Coordinate System

[IMAGE]

By default, the light source position is the same as the viewing position specified by the XVIEW=, YVIEW=, and ZVIEW= options. The light source position cannot coincide with the viewing reference point (0.5,0.5), which corresponds with the position directly above the center of the map.
See also: XVIEW=
Featured in: Specifying Midpoints in a Prism Map

XSIZE=map-width <units>
YSIZE=map-height <units>
specify the physical dimensions of the map that is to be drawn, where n is the number of units. By default, the map uses the entire procedure output area.

Valid units are CM (centimeters), IN (inches), or PCT (percentage of the graphics output area). By default, the unit is character cells (CELLS).

If you specify values for map-width and map height that are greater than the dimensions of the procedure output area, the map is drawn using the default size. And if you specify one value and not the other, the dimension is adjusted to maintain the correct aspect ratio.

XVIEW=x
YVIEW=y
ZVIEW=z
specify the viewing position coordinates for the map. In this system, the four corners of the map lie on the X-Y plane at coordinates (0,0,0), (0,1,0), (1,1,0), and (1,0,0). No axes are actually drawn on the maps that are produced by PROC GMAP, but imagine that the maps are drawn in an X-Y plane.

Your viewing position cannot coincide with the viewing reference point at coordinates (0.5,0.5,0), the center of the map. The value for z cannot be negative.

If you omit the XVIEW=, YVIEW=, and ZVIEW= options, the default coordinates are (0.5,-2,3). This viewing position is well above and to the south of the center of the map. Specify one, two, or all three of the view coordinates; any that you do not explicitly specify are assigned the default values.

Viewing Position and Viewing Reference Point shows the position of the viewing reference point, as well as the default viewing position.

To ensure that the polygon edges are distinguishable, the angle from vertical must be less than or equal to 45 degrees. If you specify a ZVIEW= value such that this condition cannot be satisfied (that is, a very small value), PROC GMAP increases the ZVIEW= value automatically so that the angle is 45 degrees or less.
Featured in: Specifying Midpoints in a Prism Map


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Copyright 1999 by SAS Institute Inc., Cary, NC, USA. All rights reserved.