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The GMAP Procedure

SURFACE Statement

Creates three-dimensional surface maps in which levels of magnitude of the specified response variables are represented by spikes of varying height.

Requirements: At least one response variable is required and must be numeric. The ID statement must be used in conjunction with the SURFACE statement.
Global statements: FOOTNOTE, TITLE


The SURFACE statement specifies the variable or variables that contain the data that are represented on the map by raised map areas. This statement automatically determines the midpoints. You can use statement options to control spike proportions, specify the angle of view, and modify the general appearance of the map. For example, you can select the color and number of lines for the representation of the surface area. You can control the selection of spike heights and base widths.

In addition, you can use global statements to add titles and footnotes to the map. You can also use an Annotate data set to enhance the map.
SURFACEresponse-variable(s) </ option(s)>;

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

Required Arguments

specifies one or more variables in the response data set that contains response values for map areas in the map data set. Response-variable must be numeric and must contain only positive values. Each response variable produces a separate map. All variables must be in the input data set. Separate multiple response variables with blanks.

The GMAP procedure scales response variables for presentation on the map. The height of the spikes on the map correspond to the relative value of the response variable, not to the actual value of the response variable. However, when the viewing angle is changed, the spikes may not appear this way. The spikes in the front may appear to be higher than the spikes in the back, which represent greater values.
See also: About Response Variables


SURFACE statement options affect all maps that are produced by that statement.

specifies a data set to annotate maps that are produced by the SURFACE statement.

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

specifies the color that is used to draw the surface map. By default, the first color in the current colors list is used.

specifies a denominator to use in the distance decay function. This function determines the base width of the spike that is drawn at each map area center.

By default, CONSTANT=10. Values greater than 10 yield spikes that are wider at the base. Values less than 10 yield spikes that are narrower at the base.

Let xk and yk represent the coordinates, and zk represent the function value at the center of each map area. The zk values are scaled from 1 to 11. A square grid of x by y points (where the size of the grid is the NLINES= option value) and the associated function value f(x,y) are generated from the map area center value using this formula:






Featured in: Rotating and Tilting a Surface Map

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

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 the specified name 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.

specifies the number of lines, n, used to draw the surface map. Values for n are 50 to 100; the higher the value, the more solid the map appears and the more resources used. By default, NLINES=50.
Featured in: Rotating and Tilting a Surface Map

specifies the degrees of the angle at which to rotate the map about the Z axis in the map coordinate system. Degrees can be any angle. Positive values indicate rotation in the counterclockwise direction. By default, ROTATE=70. The ROTATE= option also affects the direction of the lines that are used to draw the surface map.
Featured in: Rotating and Tilting a Surface Map

specifies the degrees of the angle at which to tilt the map about the X axis in the map coordinate system. Degrees can be 0 to 90. Increasing values cause the map to tilt backward and makes the spikes more prominent. Decreasing values make the map shape more distinguishable and the spikes less prominent. TILT=90 corresponds to viewing the map edge-on, while TILT=0 corresponds to viewing the map from directly overhead. By default, TILT=70.
Featured in: Rotating and Tilting a Surface Map

XSIZE=map-width <units>
YSIZE=map-height <units>
specify the physical dimensions of the map 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 only one dimension, the other is scaled to maintain the aspect ratio.

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