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Tactician Techniques
Using Overlays to Aggregate Data for Geographic Areas
You can summarize, average, or find the minimum or maximum values of data and display them, all right from an overlay. Tactician creates the values you designate on the fly and gives you immediate results on the map.
For example, if your data document contains store locations, the postal code for each store, and sales data for each store, you can sum data by postal code and map the total sales per postal code.
Benefits include:
- Eliminate the need to summarize data to the geographic level that you need before mapping. Using the Sum operator in the Overlay summarizes on the fly.
- Keep your data documents simple. With the ability to generate sums, averages, minimums and maximums in the overlay, you don’t have to store all those variables in your spreadsheet documents.
To use the Join to Cartographic Layer feature, you must:
- Have a document that contains a geographic identifier field, and at least one numeric attribute variable.
To create the overlay:
- Open the data document that contains the geographic identifier and the attribute data.
- Open the mapview in which you want to display the data.
- Select Document>Overlays.
- Click
 to add a new overlay.
- Use the Cartographic Layer list to select the layer that matches the geographic identifier in your file. For example, if your file contains postal codes, select postal codes as the cartographic layer.
- Click OK.
- Click
 to modify the new overlay.
- In the Overlay Type list, select Classified Areas.
To aggregate the data:
- Select the Data Tab.
- Use the Document list to select the document that contains data for geographies.
- Use the Sheet type list to select the sheet in which the data is stored.
- In the Condition for displaying records section, you can optionally enter an expression to limit geographies displayed.
- In the Join to Cartographic layer… section use the Key Variable list to select the variable that contains the geographic identifier that will be joined to the cartographic layer for this document.
- In the Aggregated by list, select the operation to use to aggregate the data. Select
- Average – to compute and display the average data value for the geography.
- Sum – to compute and display the sum of data values for the geography.
- Minimum - to compute and display the minimum data value for the geography.
- Maximum – to compute and display the maximum data value for the geography.
To set classification options:
- Click the Classification tab.
- In the Expressions to Classify section, click the . The Expression dialog box displays.
- Use the Variable list to select the variable you want to classify and click OK.
- Use the Classification Method list to select the classification method for your variable. For more information about classification methods, see the Classify Command in Tactician One onine help.
- Use the # classes list to select the number of classes into which you want data values broken.
- Use the Round By list to select how you want data values rounded.
- To see how the data will be classified with these settings, click Preview Classification. When you are done viewing the classification, click OK.
To select colors for data ranges:
- Click the Style Tab.
- Click Select from Dictionary and select the color scheme for the classification.
- Click OK.
- In the Overlays dialog box, click OK. The overlay displays the geographies colored by aggregated variable value.
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