Pitney Bowes MapInfo Professional - Manual (Page 292)

Table Variables
If the table containing the selected table and the editable table are either the same table, or contain the
exact same table structure (same number of columns with each column in both tables having the same
name and data type), then the Sum and Average radio buttons do not display. The data is taken from
the current selection, and the results are placed in the editable layer.
If the table containing the selection objects and the editable table are different, and the table structures
are different, then the Sum and Average radio buttons are displayed. In this case, the data aggregation
for the editable destination table column is initially blank, and you need to select the column from the
input selection table to derive the data from.
Saving your Buffer as a New Layer
You can create a buffer and save it as a new table (layer) or as part of another layer in your map. See
Saving your Voronoi Polygon as a New Layer in the Help System. This process is also similar to the
Combine Using Column process, except that there is no "Group By" functionality for buffers.
The table must be mappable to use this feature. Note:
To create the buffer as a distinct layer:
1. To create a selection to buffer, select the object in the map. This step is not required if you want to
buffer all objects in a particular table.
2. On the Table menu, click Buffer. The Table Buffer dialog box displays.
3. Do one of the following:
• To buffer the selected object, leave the Selection object selected in the Buffer objects in table
drop-down list box.
• To buffer objects from a particular table, select the table in the Buffer objects in table drop-down
list box.
4. Select the type of table you want to place the buffer into from the Store results in Table drop-down
list box. Select one of the following:
• New table - allows you to save the buffer in a new table
• <tablenames> - allows you to save the buffer in one of the currently open tables
After you make this selection, click Next to continue.
You cannot save a buffer to the Cosmetic Layer. Note:
5. Do one of the following:
• If you chose the New table option, go to Saving a Buffer to a New Table in the Help System.
• If you chose <tablenames>, go to Saving a Buffer to an Existing Table in the Help System.
Buffer Radius
The buffer radius determines the dimensions of the buffer region. For example, if you want to create a
region that covers an area one mile on either side of a freeway, set your buffer radius to 1 mile. If you
choose to use a field from the table or an expression, MapInfo Professional will calculate the radius of
the buffer based on that value.
You can set the radius to be a constant value or you can choose a data value from the table to be used
as the radius. For example, to create buffers around major cities that reflect the size of their population,
choose the population field as the value.
You can go even further to calculate the buffer radius using an expression. For instance, you want to
create buffers around cities showing the population density. Since you do not have a field containing
population density, you will need to write an expression that can calculate density from population and
area. This is no different than writing an expression for thematic mapping or query selection.
Buffering - Setting the Number of Segments per Circle
MapInfo Professional 12.5 292
Buffering Your Data