Choose the map layer on which you want to base the map, and the field or expression from which you want to obtain the data values (thematic variable).
A thematic variable can be the data value that is associated with the graphic objects (regions, lines, and points) displayed in your map, such as the values in a column like Pop_1990, Buy_Power, or Median Age.
You can also obtain your thematic variable from another table using the Update Column command (located on the TABLE tab in the Editgroup). Update Column creates a temporary column in your base table where you can aggregate or calculate information about your data.
You can also use an expression for your thematic variable. For example, you could use the following expression to display population density:
Pop_1990/Area(obj, "sq mi")You can access the Expression dialog box in Create Thematic Map - Step 2 of 3 dialog box. See the Help topics, Using Expressions in a Thematic Map and Creating Expressions for more information.
Your map may have more than one variable, depending on the thematic method you choose. Pie and Bar chart maps contain more than one variable; the other five types of thematic maps contain one variable. Depending on your choice of a one-variable or multi-variable thematic map, one of two Create Thematic Map - Step 2 of 3 wizard panel displays.
One-Variable Thematic Maps
Ranged, graduated symbol, dot density, individual value, and grid thematic maps examine one variable. The Create Thematic Map - Step 2 of 3 wizard panel that displays for these kinds of maps asks you to choose only a table and one field or expression.
- Choose a table from the Table drop-down list. The drop-down list displays the tables that are mapped in the active Map window.
- Choose the table on which you want to base the map.
If you have objects selected in the Map window, the Selection from TABLE item also displays in the list. This enables you to create a thematic map based on the selected items without having to map the selection. You can also base your thematic map on a mapped query table.
- Choose a field from the Field drop-down list.
The drop-down list displays all the numeric fields in the table you selected from the Table list. Choose the field or expression that contains the data values.
- Select the Ignore Zeroes or Blanks check box to ignore zero values and blank values in the table.
Because you are creating a thematic map based on one field in a table, any zero or blank values in that field will cause the whole record to be ignored. If you are creating a grid map, you can choose a table of regions to clip the grid against.
- Click Next to go on to Step 3 - Customizing Your Thematic Map.
Multi-Variable Thematic Maps
Pie and Bar Chart thematic maps allow you to analyze more than one variable at a time. In the Create Thematic Map - Step 2 of 3 wizard panel, you choose the fields or expressions you want to use as the variables, and list them in an order that best suits your analysis.
Start by choosing a Pie Chart or Bar chart in the Create Thematic Map - Step 1 of 3 dialog box.
- In the Create Thematic Map - Step 2 of 3 dialog box, choose the table on which you want to base the map from the Table drop-down list.
The drop-down list displays the tables that are mapped in the active Map window.
If you have objects selected in the Map window, the Selection from TABLE item also displays in the list. This enables you to create a thematic map based on the selected items without having to map the selection.
Fields from TABLE displays all the numeric fields in the table you selected from the Table list.
- Choose the field, or create an expression that contains the data values.
Fields for Pie/Bar Chart indicates the fields or expressions you have chosen for your pie or bar chart thematic map. The order of the variables in the Field for the Pie/Bar Chart list is the order in which the variables appear in the legend.
- For bar chart thematic maps, the order in which the variables display in the legend is the order in which the bars display from left to right on the map.
- For pie chart maps, the first variable in the legend corresponds to the pie wedge that begins at the angle specified in the Customize Pie Style dialog box.
- Click Styles in the Create Thematic Map - Step 3 of 3 wizard panel.
The Customize Pie Style dialog box opens:
- Click Up to move the selected field or expression up one place in the Fields for Pie/Bar Chart list. Up is unavailable when the selected item is the first item in the list.
- Click Down to move the selected field or expression down one place in the Fields for Pie/Bar Chart list. Down is unavailable when the selected item is the last item in the list.
- Click the Right Arrow button to move the selected field in the Fields from TABLE list to the Fields for Pie/Bar Chart list.
- Click the Left Arrow button to move the selected field in the Fields for Pie/Bar Chart list to the Fields from TABLE list.
- Click Next to go on to Step 3.