Pitney Bowes MapXtreme - Manual (Page 284)

Chapter 14: Using Themes and Legends
Legends Overview
MapXtreme v7.1 291 Developer Guide
Bivariate Thematic Maps
Bivariate thematic mapping uses point or line objects to represent two thematic variables. For
example, a star can represent one variable, such as the number of teenagers, while a blue fill for the
star represents their annual purchase amounts.
To create a bivariate map in MapX, you create two thematic maps, and layer one over the other so
that the objects display two variables.
Types of Maps and Variables
The only types of thematic maps suitable for bivariate mapping are ranged and individual values
maps. You can choose between two combinations for a bivariate map, depending on your data:
• two ranged maps
• one ranged map and one individual values map
If you have a non-numeric variable, one of your maps must be an individual values map. You cannot
create a bivariate map with two non-numeric variables.
Displaying Attributes
To display two variables within one symbol, it is important to choose a different symbol attribute for
each variable. For example, you cannot choose color for both variables because one color will
overwrite the other. Choose from the following combinations:
• color and symbol type
• color and size
• size and symbol type
Symbol type should only be used for nominal or non-numeric data, as there is no inherent
association between a symbol type and a quantity.
VB example:
Public Shared Sub MapInfo_Mapping_Thematics_RangedThemeConstructor(ByVal
lyr As FeatureLayer)
Dim thm As MapInfo.Mapping.Thematics.RangedTheme = New _
MapInfo.Mapping.Thematics.RangedTheme(lyr, “Literacy”, “Pop_1994”, _
“Literacy Quantile by Pop”, 4)
lyr.Modifiers.Append(thm)
End Sub
Legends Overview
The MapInfo.Mapping.Legends namespace contains classes, interfaces and enumerations for
creating and displaying thematic and cartographic legends. Legends are a collection of Thematic or
Cartographic LegendFrames. Each frame contains a collection of LegendRows, Each LegendRow
has text and a style property.