Overview of Combining Map Objects - MapInfo_Pro - 2023

There are two Combine operations:

1. Combine Selected Objects: MapInfo Pro geographically combines the selected objects. The new object represents the geographic union of the original objects. Therefore, if you select two adjacent region objects and choose Combine, MapInfo Pro combines the regions into a single object, and the border between the regions disappears.
2. Combine Using Column: MapInfo Pro performs data aggregation. Data aggregation is a process where MapInfo Pro calculates what the column values for the new object should be, based on sums or averages of the values of the original objects.

Perhaps you have a table of sales territories, and the table contains demographic information about the number of households per territory. Using the Combine commands, you can combine two of the sales territories into one, large territory. In the same operation, MapInfo Pro also can calculate the number of households in the new territory by adding the values from each of the original territories.

Combining Objects with Set Target

The Combine operation can work in conjunction with the target feature selected in the Edit group on the SPATIAL tab. Before you choose a Combine command, you can select one map object and designate that object as the editing target. You can then select additional map objects and choose Combine Selected Objects to combine the selected objects with the target. If you set a target before you choose Combine Selected Objects, the operation is more flexible, allowing you to combine objects from different tables.

You should assign a target object if one of the objects you are combining is more important than any of the other objects. For example, if you want to add small, unnamed islands to an existing "mainland" region, you should make the mainland region the target object. If you designate the mainland region as the target, MapInfo Pro is able to retain the mainland region's name after the objects are combined.

Using a Combine command with the Set Target command allows the mainland region to retain its name after the objects are combined. You can only set one object as the target at a time when using a Combine command with Set Target. The modifying object can consist of more than one object.

Keep in mind that the Combine Selected Objects command works with selected map objects. To apply the Combine operation to an entire table, select everythng in the map by pressing Ctrl+A. To combine into groups rather than objects, or output to a separate table, use the Combine Using Column command.

To combine map objects using Set Target:

1. Select one object in an editable layer to be the target object.
2. On the SPATIAL tab, in the Edit group, click Set Target. The object displays in a different style to indicate that it is the target object.
3. Select (or create and select) one or more map objects from any layer in the Map window. This is the modifying object.
4. On the SPATIAL tab, in the Edit group, click Combine, and Combine Selected Objects to open the Data Aggregation dialog box.
5. Choose the appropriate aggregation method (or No Data) for each field in the Destination list. See the definitions for these methods in Aggregating and Disaggregating Data.
   Note: To select more than one field in the Data Aggregation dialog box at a time, use these keystrokes:
   • Shift-click to apply the same method to consecutive fields
   • Ctrl-click for non-consecutive fields.

     When you have chosen the aggregation methods for each field, click OK.

     

6. Select one or more columns by clicking in the list at the top of the Data Aggregation dialog box.
7. Choose a data aggregation method: Blank, No Change, Value, Sum, Average, or Weighted Average. (Depending on whether you specified an editing target, some of these aggregation methods may not be available.) MapInfo Pro updates the column list in the upper half of the dialog box to show the chosen method.
   • For example, if you choose Average, you are telling MapInfo Pro to calculate the average of the column values of all the selected objects. This average is stored in the column of the new row.
   • Aggregation methods are described below.
8. Repeat steps 6 and 7 for all columns in your table and click OK.
   • To simplify this process, select multiple columns at one time by Shift-clicking and/or Ctrl-clicking in the list of columns. If you select multiple columns, and then choose an aggregation method, MapInfo Pro applies that method to all selected columns.

If your table contains a large number of columns, it can be time-consuming to specify aggregation methods for all columns. However, MapInfo Pro remembers your aggregation methods for the remainder of your session; thus, the next time you choose a Combine command, you do not need to respecify all aggregation options.

MapInfo Pro computes the new object and displays it as a single object. Use the Info command to view the aggregated data (if any) associated with the object.

Combining Points, Linear, and Closed Objects into a Single Object

Combine points, linear, and closed objects into a single (collection) object by selecting points and performing a Combine operation. The collection object displays in the Browser as a single record.

All line, polyline and arc objects, as well as the polyline component of any collection objects that exist in the input will be combined to form a new polyline object.

All regions, rectangles, rounded rectangles, and ellipses, as well as the region component of any collection objects, that exist in the input will be combined to form a new region object.

To create a collection object:

1. Select two or more points from the editable layer of the active Map window.
2. On the SPATIAL tab, in the Edit group, click Combine, and Combine Selected Objects.

   The points are combined into a single object.

To specify object attributes for a collection object, double-click on the collection object to display the Collection Object dialog box.

Specifying Collection Object Attributes

A collection object is the result of combining points, linear, and closed objects into a single object.

The collection object must be editable (reside in an editable layer) before you can specify attributes.

1. Make the layer containing the collection object editable.
2. Do one of the following:
   • Select a collection object and press F7 to open the Collection Object dialog box.
   • Double-click the collection object to open the Collection Object dialog box.
3. Specify attributes for the collection object.
4. Click OK.

Default Data Aggregation Methods

When the Data Aggregation dialog box first opens, MapInfo Pro automatically assigns a default aggregation method to every column in the table. For numeric columns (Integer, Small Integer, Float, or Decimal), MapInfo Pro assigns Sum as the default aggregation method. For all other types of columns, MapInfo Pro assigns Value as the default method.

You could simply choose OK, without changing any of the default aggregation methods. However, there is no guarantee that the default aggregation methods will produce meaningful results. By default, MapInfo Pro uses the Sum method for all numeric columns; however, depending on your data, it may not make sense to total all of your columns.

For example, perhaps your table contains demographic information, such as median income statistics. If two adjacent regions have different median income values ($30,000 and $35,000), and you combine the two regions, it does not make sense to total the two values; instead, you should choose Average or Weighted Average as the aggregation method.