Table of Contents
TGIS_ClassificationAbstract class
DK11 for Delphi | GisClassification.TGIS_ClassificationAbstract | Classes | Methods | Properties
General class that enables performing advanced data classification in the process of creating choropleth (thematic) maps. Must be derived.
Syntax
// Delphi type TGIS_ClassificationAbstract = class( TGIS_Object ) end;
// C++ Builder class PASCALIMPLEMENTATION TGIS_ClassificationAbstract : public TGIS_Object { };
Inheritance
Methods
| Name | Visibility | Description | |
|---|---|---|---|
| AddClassBreak | public | Adds a new class break. | |
| Classify | public | Performs the classification. | |
| Classify(TGIS_ParamsList) | public | Performs the classification and applies to defined ParamsList. | |
| doCreate | protected | Internal constructor. | |
| EstimateNumClasses | public | Performs the pre-classification and sets NumClasses property. | |
| MustCalculateStatistics | public | If True, statistics from layer assigned to classification need to be calculated. | |
Properties
| Name | Visibility | Description | |
|---|---|---|---|
| ClassBreaks | public | Computed class breaks. | |
| ColorRamp | public | The color ramp that is used to assign colors for class breaks; none by default If not provided, StartColor and EndColor will be used. | |
| ColorRampName | public | The name of the built-in color ramp that is used to assign colors for class breaks; empty by default. | |
| EndColor | public | Ending color used to generate ramp for class breaks; Black by default. | |
| ForceStatisticsCalculation | public | Forces the calculation of layer statistics; True by default. | |
| Interval | public | Class interval size; default value is 1. | |
| Layer | public | Layer assigned to object. | |
| Method | public | Classification method; NaturalBreaks by default. | |
| NumClasses | public | Number of classes; default is 5, max is 30. | |
| ShowLegend | public | If True, features will be shown in legend panel; True by default. | |
| StartColor | public | Starting color used to generate ramp for class breaks; White by default. | |
| Target | public | Indicates the data to be used for classification; empty by default. | |
Remarks
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This class can be used for data classification in process of creating thematic maps.
The main purpose of data classification is to group large number of observation into classes according to classification method and it's parameters (NumClasses or Interval).
The layer's attributes used in classification must have numerical values that are real or integer type. Name of the attribute field is specified in TGIS_ClassificationVector.Field property (1), or TGIS_ClassificationPixel.Band (2).
Generated class breaks are stored in ClassBreaks indexed property. Furthermore, information about belonging to classes for each observation can be written in attribute field provided in TGIS_ClassificationVector.ClassIdField (1).
StartColor, EndColor, TGIS_ClassificationVector.StartSize (1), and TGIS_ClassificationVector.EndSize (1) properties limit the range of generated visual properties - color ramp or size/width - depends on layer type defined TGIS_ClassificationRenderType.
Here is a list of available classification methods, commonly used by GIS specialists:
and less frequent but very useful:
Data classification process can affect different visual layer's properties,look at the following enum:
(1) applies only to vector layers, (2) applies only to pixel layers