Using Expressions in a Thematic Map - MapInfo_Pro - 2023

The Expression dialog box builds expressions and uses them as the thematic variable(s) in your map. You can use more than one expression per bar or pie thematic map. Instead of choosing a field to represent the thematic variable in Step 2 of creating a thematic map, choose Expression to access the Expression dialog box.

To access the Expression dialog box in a one-variable thematic map:

1. In the Create Thematic Map - Step 1 of 3 wizard panel, choose Expression from the Field drop-down list.
2. In the Expression dialog box, create the desired expression.
3. Click OK.

   The Create Thematic Map - Step 2 of 3 wizard panel opens. The expression is added to the Field drop-down list.

4. Repeat the above steps to create as many expressions as necessary.
5. Click Next.

   The Create Thematic Map - Step 3 of 3 wizard panel opens.

To access the Expression dialog box in a multi-variable thematic map:

1. Choose Expression from the Table drop-down list.
2. In the Expression dialog box, create the desired expression.
3. Click OK.
4. Repeat the above steps to create as many expressions as necessary.

The Create Thematic Map - Step 2 of 3 wizard panel opens. The expression is added to the Fields for Pie/Bar Chart list.

Using Automatic Joining

Whenever you specify a source table that is different from the target table in the Update Column dialog box, MapInfo Pro tries to determine how to join them. A join is first tried on the basis of tabular data. When that fails, a geographic join is attempted. When that fails, MapInfo Pro indicates that the autojoin failed.

The autojoin strategy works as follows:

• The tabular data in the two tables is compared. When matching data values are found, MapInfo Pro assumes that it has found matching fields and uses those as the basis of the join. When MapInfo Pro fails to produce a match this way, then:
• A graphic/geographic match is attempted. MapInfo Pro attempts either to locate source objects within target objects, or to locate target objects within source objects.

When a match is not produced, then:

• MapInfo Pro reports that the autojoin failed. In this case you should click Join and use the settings in the Specify Join dialog box to specify how to make the join.