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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.

Available also on: .NET | Java | ActiveX.


// Delphi
  TGIS_ClassificationAbstract = class( TGIS_Object )
// C++ Builder
class PASCALIMPLEMENTATION TGIS_ClassificationAbstract : public TGIS_Object


→ TObject → TGIS_Object


Inherited Overrides Protected
Name Visibility Description
Classify public Performs the classification.
Classify(TGIS_ParamsList) public Performs the classification and applies to defined ParamsList.
doCreate protected Internal constructor.
MustCalculateStatistics public If True, statistics from layer assigned to classification need to be calculated.


Inherited Protected
Name Visibility Description
ClassBreaks public Computed class breaks.
ColorRamp public The color ramp used to generate colors for class breaks.
EndColor public Ending color used to generate ramp for class breaks.
Interval public Class interval size; default 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.
StartColor public Starting color used to generate ramp for class breaks.
Target public Indicates the data to be used for classification.


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


2020/07/03 22:23

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