ArcObjects Library Reference (Carto)

IClassBreaksRenderer Interface

Provides access to members that control a renderer which is used to draw graduated color (choropleth) and graduated symbol maps.

Product Availability

Available with ArcGIS Engine, ArcGIS Desktop, and ArcGIS Server.

Description

IClassBreaksRenderer defines the parameters for drawing features based on the values of a quantitative attribute that is statistically grouped by a classification algorithm.

When To Use

Use this interface to make changes to the drawing properties of a ClassBreaksRenderer.

Members

		Description
	BackgroundSymbol	Background fill symbol used when graduated marker symbols are draw on polygon features.
	Break	Break value at the specified index. Break(0) is the lowest break and represents the upper bound of the lowest class.
	BreakCount	Number of class breaks (equal to the number of classes).
	Description	Description at the specified index.
	Field	Classification field.
	Label	Label at the specified index.
	MinimumBreak	Minimum break, i.e. the lower bound of the first class.
	NormField	Normalization field.
	SortClassesAscending	Indicates if classes are displayed in increasing order in legends/TOC.
	Symbol	Symbol at the specified index (used to draw features in the specified class).

CoClasses that implement IClassBreaksRenderer

CoClasses and Classes	Description
ClassBreaksRenderer	A renderer that can be used to draw graduated color (choropleth) and graduated symbol maps.
NetworkTrafficRenderer	A renderer used to display network dataset traffic.

Remarks

To set up a ClassBreaksRenderer you first need to know how many classes you will have. You can decide this arbitrarily, or you can pass a proposed number of class breaks to a classification object and then have it return a valid number of breaks for your data and the classification method that you chose. To learn more see IClassifyGen. Set the number of class breaks using BreakCount.

Once BreakCount is set, the Break, Description, Label, and Symbol array properties are initialized with a lower index index of 0 and an upper index of BreakCount -1.

The next step is to set the values in Break, which are referred to as the class breaks. These values define the classes. Before setting your class breaks, you should understand the characteristics of your data. One possibility is that you may have predefined class breaks in mind, for example you might classify temperature data into 10 classes of 10 degrees each.

More commonly, you will apply a particular classification algorithm (e.g. natural breaks, quantile, equal interval) to your data and use the breaks generated from the algorithm to assign to your renderer. The easiest way to do this is to use a histogram object such as a TableHistogram, and a classification object such as NaturalBreaks. To learn more, see IClassifyGEN.

Once you have decided on your breaks, assign them to your renderering using the Break array property. You should set MinimumBreak to the lowest value in the data that you want to symbolize, and then Break(i) represents the highest value in the ith class. Values less than or equal to Break(i) but greater than Break(i-1) will be drawn with Symbol(i). To learn more see Break and Symbol.