Creating a Voronoi Polygon - MapInfo_Pro - 2023

The Voronoi polygon is a partition of space into cells. Voronoi takes points and produces regions (cells) as output where each cell contains exactly one point. Each cell is an area in which the contained points are closer to the enclosed site than to any others. Use Voronoi to generate these polygons from a designated set of points. It is useful for dividing areas of responsibilities for field offices or possibly postal zones. It ultimately gives you the areas that are closest to your point of interest. You can create a Voronoi polygon within the same layer, or select points from one layer and place the Voronoi polygon in another layer.

To create a Voronoi polygon:

1. Select at least three points. The Voronoi polygon is constrained by the bounding box of the selected points. You can also use a target region to constrain the size of your polygon.
2. On the SPATIAL tab, in the Create group, click Regions, and Voronoi (Objects) to open the Data Aggregation dialog box.

   To save the Voronoi polygons you create to a new table, see Saving your Voronoi Polygon as a New Layer.

3. Select a column from the list and select the data aggregation method for that column by selecting one of the following:
   Note: Not all of these data aggregation methods display. The options depend upon the kind of data you are aggregating and whether the columns match.
   • Click Blank to store blank values in the selected columns.
   • Click Value to enter an appropriate value to be stored in the new row.
     Note: You can specify the data aggregation method to be performed for one column or for more than one by following these directions:
   • Click a column name to select a single column
   • Shift-click columns to select contiguous column names and apply the selected aggregation method to all of them
   • Ctrl-click to de-select a column
     Note: To create a voronoi table of the selected objects with no data in them, click the No Data check box. Selecting this check box disables the column selection in the Data Aggregation list.
     
     

     

     
     

     This is a sample of a Voronoi polygon based on the capitals in northern Africa.

Saving your Voronoi Polygon as a New Layer

The Table Voronoi operation provides an another way to create Voronoi polygons from a table and provides a mechanism to place the results into a new table. This process is not directly available using the Objects Voronoi operation.

To set up a Voronoi polygon in new table or in an existing table:

1. Open and display the table for which you want to create Voronoi polygons.
   Note: If you want to use a selection to create the Voronoi polygon, hold down the Shift key and select the points you want. This is not required. If you do not make a selection at this point, MapInfo Pro will use all of the points on the selected layer to create the polygon.
2. To create a boundary for the Voronoi polygon layer you are creating, use the Target Object feature described in Adding Nodes to an Object. This is not required.
3. On the SPATIAL tab, in the Create group, click Regions, and Voronoi (Objects) to open the Data Aggregation dialog box.
4. Select the layer you want to create the Voronoi polygon with in the Perform Voronoi using objects from table drop-down list. If you selected points you want to use to create this polygon, choose the Selection entry in this list.
5. Select the table type for the results of the Voronoi polygon from the Store results in table drop-down list:
   • New table - allows you to save the Voronoi polygon in a new table
   • tablenames - allows you to save the Voronoi polygon into one of the currently open tables that contain point objects
6. After you make this selection, click Next to continue. Do one of the following:
   • If you selected the New table option, go to Save the Voronoi Polygon to a New Table.
   • If you selected the <tablenames> option, go to Save the Voronoi Polygon to an Existing Table.

Save the Voronoi Polygon to a New Table

To save the Voronoi Polygon to a new table:

1. In the New Table dialog box, follow these directions:
2. Use the New Table check boxes to indicate where you want the new Voronoi polygon to display. You can click more than one option. The options include:
   • Open New Browser - Click this check box to display the new Voronoi polygon in a new Browser window only.
   • Open New Mapper - Click this check box to display the new Voronoi polygon in a new Map window.
   • Add to Current Mapper - Click this check box to display the new Voronoi polygon in the current Map window.
3. Choose one of these options to specify the table structure for the new table:
   • Create New - Click this option to create a new table structure and add the new fields in the New Table Structure dialog box.
   • Use Table - Click this option to create the new table structure based on the fields in an existing table. You can base your new table structure on any open table.
4. Click Create. The New Table Structure dialog box displays.
   
   

   

   
   

   Click the Projection button to set the projection for this table. For more about Projections, see Coordinate Systems, Projections, and their Parameters.

   Note: If there are entries in this dialog box, you are copying the table structure of an existing table. If you opted to create a new table structure, there are no fields to list.
5. In the New Table Structure dialog box, you can add and remove fields to create a new table structure. Click the Add button and type a name, field type, and field width in the fields and drop-down list provided to create a new field in the new table.
6. When you have completed the table structure, click Create to create the table and display the Voronoi polygon according to the display settings you specified. The Create New Table dialog box opens so you can save the name of the new table.
7. Type the name you want the new table to have in the File Name field and click Save to save it. You can choose a new directory in this dialog box as well.

Save the Voronoi Polygon to an Existing Table

1. When you choose to store the table results in the existing table, the Data Aggregation box opens.
   1. Select the field from the Destination list.
   2. Specify the data Aggregation Method to use.
   3. If the columns in the tables you are combining do not match, specify the source column in drop-down list (located to the right of the Value field).
      Note: If you selected tables with disparate values, there may be additional fields in this dialog box. You need to reconcile these table values using this dialog box.
2. To specify the data aggregation you want MapInfo Pro to use to create the new table structure, highlight each field in turn and do one of the following:
   • Blank - Use this option to indicate that this field should remain blank.
   • Value - Use this option to indicate that this field should contain a specific value or should retain its existing value. If the field should contain a specific value, enter that value into the Value field.
     Note: Other aggregation methods may be available based on the data columns in the tables. See Aggregating and Disaggregating Data for these details.
3. If the new table information should add no data to the existing table, select the No Data check box to disable the other field options.
4. After you have completed these selections and entries, click OK.