Pitney Bowes MapInfo Professional - Manual (Page 262)

Using Data from the Same Table
If you are using data from the same table, choose the table and field on which you want to base your
thematic map in the Create Thematic Map - Step 2 of 3 wizard panel.
For example, you have a table of parking meters that contains the location of the parking meter and the
last time the parking meter was emptied. Using Individual Values you want to shade the parking meter
symbols according to the last time each meter was emptied. MapInfo Professional will assign a color to
each time. In the Create Thematic Map - Step 2 of 3 wizard panel, choose the parking meter table as
your table, and choose the field that contains the time each meter was emptied.
Using Data from a Different Table
The Join feature within the Create Thematic Map - Step 2 of 3 wizard panel enables you to use data
from other open tables to create a thematic map. Choose Join in the Field list box to display the Update
Column dialog box where you can create a temporary column in the base table.
The temporary column can contain data taken directly from the other table, or you can aggregate the
data to create derived information for the temporary column.
For example, you have two tables: a table of county boundaries and a table of police stations. You want
to shade the table of county boundaries according to the number of police stations in each county.
To do this, all the information you want to use must be in the county table. Therefore, you must add
police station data to this table.
Using Update Column, you create a temporary column in the county boundaries table that will store the
police station information. To create this column, the two tables must have a link so that MapInfo
Professional can access the data that goes into the temporary column. The link can either be a matching
field (like county name), or you can make the link geographically (police stations contained within counties).
An example later in this chapter explains more about Update Column.
Methods of Thematic Mapping
When you create a thematic map in MapInfo Professional, the thematic shading is added to your map
as a separate layer. It is drawn on top of the base map layer.
Separating Thematic Layers
Separating thematic layers from the base map layer provides you with several important options:
• Graduated symbol thematic maps do not require that your base map contain point objects. Instead,
graduated symbol objects are built regardless of the map object type. Therefore, even if your base
map contains region or line objects, you will still be able to create a graduated symbols map.
• You can have multiple thematic layers per base map layer. In some cases, you do not have to add
another base layer to the map to create another thematic layer. You can display more than one thematic
layer at a time, as well as perform bivariate thematic mapping.
• You can use Layer Control to turn the display on or off for a given thematic layer. The layer it is based
on can continue to display. You can also set individual zoom layers on thematic maps.
Ordering of Thematic Layers
To display thematic layers properly, they must be in a specific order. This is especially important when
you want to display more than one thematic layer at a time. For example, you would want pie or bar
charts for an area map to display on top of regions that are shaded in order to see them.
The following lists the order of map layers from top to bottom (note that map layers are drawn from the
bottom up):
1. Pies, Bars, or Graduated Symbol thematic layer.
2. Dot Density thematic layer.
3. Ranged thematic layer - where Color or Size Attributes are applied.
MapInfo Professional 12.5 262
Using Thematic Mapping to Analyze Information