Pitney Bowes MapInfo Professional - Manual (Page 295)

list, and use the style buttons to change the fill pattern and line style for the buffer. You can also collect
data within each buffer ring using the Calculate Ring Statistics button.
Convex Hull Buffers
The Convex Hull command provides another means of creating a polygon around a selected object or
objects. Convex Hull is similar to creating a buffer in several ways. Like a buffer, the Convex Hull command
always creates an object from the input objects, and it will place the result objects into the editable layer.
In addition, you have a choice to create one convex hull object from all of the input objects, or to create
one convex hull object for each input object.
The resulting region object(s) are based on the nodes from the input object. The Convex Hull operation
can be thought of as an operator that places a rubber band around all of the points. It consists of a
minimal set of points such that all other points lie on or inside the polygon. Since the polygon is convex,
no interior angles are greater than 180 degrees. No attribute data is aggregated in this operation. To
use Convex Hull, a Map window must be active, it must have an editable layer, and objects in the editable
layer must be selected.
To create convex hull objects:
1. On the Objects menu, click Convex Hull. The Create Convex Hull dialog box displays.
2. Select the type of convex hull objects you want to create. You have two options:
• One output object for all input objects button is the default setting. It creates one convex hull
object around all of the selected objects.
• One output object for each input object button creates a convex hull object around each selected
object.
3. Click OK. Your map redisplays. The convex hull object(s) is displayed over the input objects. If you
want to save this data, save the editable table. The convex hull object is selected when it displays.
4. To change the fill of the convex hull object, do one of the following:
• Double-click it to display the Region Object dialog box. Click the Style icon at the bottom of the
dialog box to display the Region Style dialog box. Make any changes you like and click OK.
• Select the convex hull object, if it is not already, and on the Options menu, click Region Style.
The Region Style dialog box displays. Make the changes you want and click OK.
Editing Objects using the Set Target Model
With MapInfo Professional's advanced set target editing functionality, you can combine, split, erase map
objects, and overlay nodes using a "Set Target - Apply Action" editing model. This model allows you to
use objects from the same table or another table to create new objects. Sophisticated data aggregation
methods allow you to calculate new data values that match the new objects.
The Set Target editing model in MapInfo Professional allows you to set a map object as the target for
editing, then create a modifying object that will act as the cookie cutter that overlays the target and
performs the editing action on the target. Set Target is located under the Objects menu.
Figure: Buffered retail locations showing market penetration
295 MapInfo Professional User Guide
Chapter 11: Buffering and Working with Objects