Table of Contents
TGIS_ClassificationAbstract class
DK 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 manual class break value. | |
| Classify | public | Performs classification using the assigned layer ParamsList. | |
| Classify(TGIS_ParamsList) | public | Performs classification and applies the generated style to the specified ParamsList. | |
| doCreate | protected | Initializes classifier defaults and binds the classifier to the specified layer. | |
| EstimateNumClasses | public | (Deprecated) Performs pre-classification and sets the NumClasses property. | |
| MustCalculateStatistics | public | Indicates whether statistics for the assigned layer must 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; not assigned by default. | |
| ColorRampName | public | The name of the built-in color ramp that is used to assign colors for class breaks; directly related with ColorRamp. | |
| EndColor | public | Ending color used to generate the color ramp for class breaks; Black by default. | |
| ForceStatisticsCalculation | public | Forces 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. | |
| ShowLegend | public | If True, generated classes are shown in the legend; True by default. | |
| StartColor | public | Starting color used to generate the color ramp for class breaks; White by default. | |
| Target | public | Indicates the data 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