Using Spatial Data with SAS/GIS Software

Linking the Attribute Data to the Spatial Data

Before you can use your spatial data as a basis for exploring your attribute data, you must link the attribute data to the spatial data. As explained in Introducing SAS/GIS Software, one way to use the attribute data after you have linked it to the spatial data is by creating a theme to control the appearance of features in the spatial data.

Position the pointer on the COUNTY layer name in the layer bar and press the mouse menu button to open the layer bar pop-up menu for the COUNTY layer, then select Edit... to open the GIS Layer window. In the definition for the COUNTY layer, select Thematic. The GIS Attribute Data Sets window opens for you to define the link to the theme data set.

In the GIS Attribute Data Sets window, select [New] to define a new link. In the resulting Select a Member window, select MAPS.USAAC. You must next specify the values that are common to both the attribute and spatial data, since the common values provide the connection between the spatial data and the attribute data. The spatial database and the MAPS.USAAC data set share compatible state and county codes, so first select STATE in both the Data Set Vars and Composites lists, then select COUNTY in both lists. Select [Save] to save the link definition to the Links list. Finally, select [Continue] to close the GIS Attribute Data Sets window.

After the GIS Attribute Data Sets window closes, the Var window automatically opens for you. Select which variable in the attribute data provides the theme data for this theme. Select the CHANGE variable to have the counties colored according to the level of change in the county population, and then select [OK] to close the Var window.

The counties in the spatial data are colored according to the demographic values in the attribute data set, as shown in Linking the Attribute Data as a Theme.

Linking the Attribute Data as a Theme

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Note: The theme ranges in the COUNTY layer reflect the range of values in the MAPS.USAAC data set, which contains data for the entire United States. See Chapter 5, "Customizing Maps," in SAS/GIS Software: Usage and Reference, Version 6 for details on how you can select different theme ranges that are more appropriate for the displayed counties. [cautionend]

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