An abstract class for implementations of classification methods. More...

#include <qgsclassificationmethod.h>

Inheritance diagram for QgsClassificationMethod:

[legend]

Public Types
enum	ClassPosition { LowerBound , Inner , UpperBound }
	Defines the class position. More...
typedef QFlags< MethodProperty >	MethodProperties
enum	MethodProperty { NoFlag = 0 , ValuesNotRequired = 1 << 1 , SymmetricModeAvailable = 1 << 2 , IgnoresClassCount = 1 << 3 }
	Flags for the classification method. More...

Public Member Functions
	QgsClassificationMethod (MethodProperties properties=NoFlag, int codeComplexity=1)
	Creates a classification method.
virtual	~QgsClassificationMethod ()
Q_DECL_DEPRECATED QList< QgsClassificationRange >	classes (const QgsVectorLayer *layer, const QString &expression, int nclasses)
	This will calculate the classes for a given layer to define the classes.
QList< QgsClassificationRange >	classes (const QList< double > &values, int nclasses)
	This will calculate the classes for a list of values.
QList< QgsClassificationRange >	classes (double minimum, double maximum, int nclasses)
	This will calculate the classes for defined bounds without any values.
QList< QgsClassificationRange >	classesV2 (const QgsVectorLayer *layer, const QString &expression, int nclasses, QString &error)
	This will calculate the classes for a given layer to define the classes.
virtual std::unique_ptr< QgsClassificationMethod >	clone () const =0
	Returns a clone of the method.
int	codeComplexity () const
	Code complexity as the exponent in Big O notation.
QgsClassificationMethod::MethodProperties	flags () const
	Returns the classification flags.
virtual QIcon	icon () const
	The icon of the method.
virtual QString	id () const =0
	The id of the method as saved in the project, must be unique in registry.
QString	labelFormat () const
	Returns the format of the label for the classes.
QString	labelForRange (const QgsRendererRange &range, ClassPosition position=Inner) const
	Returns the label for a range.
virtual QString	labelForRange (double lowerValue, double upperValue, ClassPosition position=Inner) const
	Returns the label for a range.
int	labelPrecision () const
	Returns the precision for the formatting of the labels.
bool	labelTrimTrailingZeroes () const
	Returns if the trailing 0 are trimmed in the label.
virtual QString	name () const =0
	The readable and translate name of the method.
const QgsProcessingParameterDefinition *	parameterDefinition (const QString &parameterName) const
	Returns the parameter from its name.
QgsProcessingParameterDefinitions	parameterDefinitions () const
	Returns the list of parameters.
QVariantMap	parameterValues () const
	Returns the values of the processing parameters.
virtual void	readXml (const QDomElement &element, const QgsReadWriteContext &context)
	Reads extra information to apply it to the method.
QDomElement	save (QDomDocument &doc, const QgsReadWriteContext &context) const
	Saves the method to a DOM element and return it.
void	setLabelFormat (const QString &format)
	Defines the format of the labels for the classes, using %1 and %2 for the bounds.
void	setLabelPrecision (int labelPrecision)
	Defines the precision for the formatting of the labels.
void	setLabelTrimTrailingZeroes (bool trimTrailingZeroes)
	Defines if the trailing 0 are trimmed in the label.
void	setParameterValues (const QVariantMap &values)
	Defines the values of the additional parameters.
void	setSymmetricMode (bool enabled, double symmetryPoint=0, bool symmetryAstride=false)
	Defines if the symmetric mode is enables and configures its parameters.
bool	symmetricModeAvailable () const
	Returns if the method supports symmetric calculation.
bool	symmetricModeEnabled () const
	Returns if the symmetric mode is enabled.
bool	symmetryAstride () const
	Returns if the symmetric mode is astride if `true`, it will remove the symmetry point break so that the 2 classes form only one.
double	symmetryPoint () const
	Returns the symmetry point for symmetric mode.
virtual bool	valuesRequired () const
	Returns if the method requires values to calculate the classes If not, bounds are sufficient.
virtual void	writeXml (QDomElement &element, const QgsReadWriteContext &context) const
	Writes extra information about the method.

Static Public Member Functions
static std::unique_ptr< QgsClassificationMethod >	create (const QDomElement &element, const QgsReadWriteContext &context)
	Reads the DOM element and return a new classification method from it.
static void	makeBreaksSymmetric (QList< double > &breaks, double symmetryPoint, bool astride)
	Remove the breaks that are above the existing opposite sign classes to keep colors symmetrically balanced around symmetryPoint Does not put a break on the symmetryPoint.
static QList< double >	rangesToBreaks (const QList< QgsClassificationRange > &classes)
	Transforms a list of classes to a list of breaks.

Static Public Attributes
static const int	MAX_PRECISION = 15
static const int	MIN_PRECISION = -6

Protected Member Functions
void	addParameter (QgsProcessingParameterDefinition *definition)
	Add a parameter to the method.
void	copyBase (QgsClassificationMethod *c) const
	Copy the parameters (shall be used in clone implementation).
QString	formatNumber (double value) const
	Format the number according to label properties.

Detailed Description

An abstract class for implementations of classification methods.

See also: QgsClassificationMethodRegistry

Since: QGIS 3.10

Definition at line 88 of file qgsclassificationmethod.h.

Member Typedef Documentation

◆ MethodProperties

typedef QFlags< MethodProperty > QgsClassificationMethod::MethodProperties

Definition at line 120 of file qgsclassificationmethod.h.

Member Enumeration Documentation

◆ ClassPosition

enum QgsClassificationMethod::ClassPosition

Defines the class position.

Enumerator
LowerBound	The class is at the lower bound.
Inner	The class is not at a bound.
UpperBound	The class is at the upper bound.

Definition at line 124 of file qgsclassificationmethod.h.

◆ MethodProperty

enum QgsClassificationMethod::MethodProperty

Flags for the classification method.

Enumerator
NoFlag	No flag.
ValuesNotRequired	Deprecated since QGIS 3.12.
SymmetricModeAvailable	This allows using symmetric classification.
IgnoresClassCount	The classification method does not compute classes based on a class count. Since QGIS 3.26

Definition at line 113 of file qgsclassificationmethod.h.

Constructor & Destructor Documentation

◆ QgsClassificationMethod()

QgsClassificationMethod::QgsClassificationMethod	(	MethodProperties	properties = NoFlag,
		int	codeComplexity = 1 )

explicit

Creates a classification method.

Parameters

properties	The properties of the implemented method
codeComplexity	as the exponent in the big O notation

Definition at line 42 of file qgsclassificationmethod.cpp.

◆ ~QgsClassificationMethod()

QgsClassificationMethod::~QgsClassificationMethod ( )

virtual

Definition at line 49 of file qgsclassificationmethod.cpp.

Member Function Documentation

◆ addParameter()

void QgsClassificationMethod::addParameter ( QgsProcessingParameterDefinition * definition )

protected

Add a parameter to the method.

The paramaeter is a processing parameter which will allow its configuration in the GUI.

Note: Only parameters having their widget implementation in C++ are supported. i.e. pure Python parameters are not supported.

Since: QGIS 3.12

Definition at line 183 of file qgsclassificationmethod.cpp.

◆ classes() [1/3]

QList< QgsClassificationRange > QgsClassificationMethod::classes	(	const QgsVectorLayer *	layer,
		const QString &	expression,
		int	nclasses )

This will calculate the classes for a given layer to define the classes.

Parameters

layer	The vector layer
expression	The name of the field on which the classes are calculated
nclasses	The number of classes to be returned

Deprecated: QGIS 3.38. Use classesV2() instead.

Definition at line 211 of file qgsclassificationmethod.cpp.

◆ classes() [2/3]

QList< QgsClassificationRange > QgsClassificationMethod::classes	(	const QList< double > &	values,
		int	nclasses )

This will calculate the classes for a list of values.

Parameters

values	The list of values
nclasses	The number of classes to be returned

Definition at line 259 of file qgsclassificationmethod.cpp.

◆ classes() [3/3]

QList< QgsClassificationRange > QgsClassificationMethod::classes	(	double	minimum,
		double	maximum,
		int	nclasses )

This will calculate the classes for defined bounds without any values.

Warning: If the method implementation requires values, this will return an empty list.

Parameters

minimum	The minimum value for the breaks
maximum	The maximum value for the breaks
nclasses	The number of classes to be returned

Definition at line 275 of file qgsclassificationmethod.cpp.

◆ classesV2()

QList< QgsClassificationRange > QgsClassificationMethod::classesV2	(	const QgsVectorLayer *	layer,
		const QString &	expression,
		int	nclasses,
		QString &	error )

This will calculate the classes for a given layer to define the classes.

Parameters

layer	The vector layer
expression	The name of the field on which the classes are calculated
nclasses	The number of classes to be returned
error	will be set to error string if an error occurred while generating the classes

Returns: list of generated classes

Since: QGIS 3.38

Definition at line 217 of file qgsclassificationmethod.cpp.

◆ clone()

virtual std::unique_ptr< QgsClassificationMethod > QgsClassificationMethod::clone ( ) const

pure virtual

Returns a clone of the method.

Implementation can take advantage of copyBase method which copies the parameters of the base class

Implemented in QgsClassificationCustom, QgsClassificationEqualInterval, QgsClassificationFixedInterval, QgsClassificationJenks, QgsClassificationLogarithmic, QgsClassificationPrettyBreaks, QgsClassificationQuantile, and QgsClassificationStandardDeviation.

◆ codeComplexity()

int QgsClassificationMethod::codeComplexity ( ) const

inline

Code complexity as the exponent in Big O notation.

Definition at line 184 of file qgsclassificationmethod.h.

◆ copyBase()

void QgsClassificationMethod::copyBase ( QgsClassificationMethod * c ) const

protected

Copy the parameters (shall be used in clone implementation).

Definition at line 54 of file qgsclassificationmethod.cpp.

◆ create()

std::unique_ptr< QgsClassificationMethod > QgsClassificationMethod::create	(	const QDomElement &	element,
		const QgsReadWriteContext &	context )

static

Reads the DOM element and return a new classification method from it.

Parameters

element	the DOM element
context	the read/write context

Definition at line 63 of file qgsclassificationmethod.cpp.

◆ flags()

QgsClassificationMethod::MethodProperties QgsClassificationMethod::flags ( ) const

inline

Returns the classification flags.

Since: QGIS 3.26

Definition at line 160 of file qgsclassificationmethod.h.

◆ formatNumber()

QString QgsClassificationMethod::formatNumber ( double value ) const

protected

Format the number according to label properties.

Definition at line 159 of file qgsclassificationmethod.cpp.

◆ icon()

virtual QIcon QgsClassificationMethod::icon ( ) const

inlinevirtual

The icon of the method.

Reimplemented in QgsClassificationEqualInterval, QgsClassificationFixedInterval, QgsClassificationJenks, QgsClassificationLogarithmic, QgsClassificationPrettyBreaks, QgsClassificationQuantile, and QgsClassificationStandardDeviation.

Definition at line 153 of file qgsclassificationmethod.h.

◆ id()

virtual QString QgsClassificationMethod::id ( ) const

pure virtual

The id of the method as saved in the project, must be unique in registry.

Implemented in QgsClassificationCustom, QgsClassificationEqualInterval, QgsClassificationFixedInterval, QgsClassificationJenks, QgsClassificationLogarithmic, QgsClassificationPrettyBreaks, QgsClassificationQuantile, and QgsClassificationStandardDeviation.

◆ labelFormat()

QString QgsClassificationMethod::labelFormat ( ) const

inline

Returns the format of the label for the classes.

Definition at line 218 of file qgsclassificationmethod.h.

◆ labelForRange() [1/2]

QString QgsClassificationMethod::labelForRange	(	const QgsRendererRange &	range,
		QgsClassificationMethod::ClassPosition	position = Inner ) const

Returns the label for a range.

Definition at line 348 of file qgsclassificationmethod.cpp.

◆ labelForRange() [2/2]

QString QgsClassificationMethod::labelForRange	(	double	lowerValue,
		double	upperValue,
		ClassPosition	position = Inner ) const

virtual

Returns the label for a range.

Reimplemented in QgsClassificationLogarithmic, and QgsClassificationStandardDeviation.

Definition at line 353 of file qgsclassificationmethod.cpp.

◆ labelPrecision()

int QgsClassificationMethod::labelPrecision ( ) const

inline

Returns the precision for the formatting of the labels.

Definition at line 222 of file qgsclassificationmethod.h.

◆ labelTrimTrailingZeroes()

bool QgsClassificationMethod::labelTrimTrailingZeroes ( ) const

inline

Returns if the trailing 0 are trimmed in the label.

Definition at line 226 of file qgsclassificationmethod.h.

◆ makeBreaksSymmetric()

void QgsClassificationMethod::makeBreaksSymmetric	(	QList< double > &	breaks,
		double	symmetryPoint,
		bool	astride )

static

Remove the breaks that are above the existing opposite sign classes to keep colors symmetrically balanced around symmetryPoint Does not put a break on the symmetryPoint.

This is done before.

Parameters

breaks	The breaks of an already-done classification
symmetryPoint	The point around which we want a symmetry
astride	A bool indicating if the symmetry is made astride the symmetryPoint or not ( [-1,1] vs. [-1,0][0,1] )

Definition at line 315 of file qgsclassificationmethod.cpp.

◆ name()

virtual QString QgsClassificationMethod::name ( ) const

pure virtual

The readable and translate name of the method.

Implemented in QgsClassificationCustom, QgsClassificationEqualInterval, QgsClassificationFixedInterval, QgsClassificationJenks, QgsClassificationLogarithmic, QgsClassificationPrettyBreaks, QgsClassificationQuantile, and QgsClassificationStandardDeviation.

◆ parameterDefinition()

const QgsProcessingParameterDefinition * QgsClassificationMethod::parameterDefinition ( const QString & parameterName ) const

Returns the parameter from its name.

Since: QGIS 3.12

Definition at line 188 of file qgsclassificationmethod.cpp.

◆ parameterDefinitions()

QgsProcessingParameterDefinitions QgsClassificationMethod::parameterDefinitions ( ) const

inline

Returns the list of parameters.

Since: QGIS 3.12

Definition at line 311 of file qgsclassificationmethod.h.

◆ parameterValues()

QVariantMap QgsClassificationMethod::parameterValues ( ) const

inline

Returns the values of the processing parameters.

One could use QgsProcessingParameters::parameterAsXxxx to retrieve the actual value of a parameter.

Since: QGIS 3.12

Definition at line 324 of file qgsclassificationmethod.h.

◆ rangesToBreaks()

QList< double > QgsClassificationMethod::rangesToBreaks ( const QList< QgsClassificationRange > & classes )

static

Transforms a list of classes to a list of breaks.

Definition at line 33 of file qgsclassificationmethod.cpp.

◆ readXml()

virtual void QgsClassificationMethod::readXml	(	const QDomElement &	element,
		const QgsReadWriteContext &	context )

inlinevirtual

Reads extra information to apply it to the method.

Reimplemented in QgsClassificationStandardDeviation.

Definition at line 171 of file qgsclassificationmethod.h.

◆ save()

QDomElement QgsClassificationMethod::save	(	QDomDocument &	doc,
		const QgsReadWriteContext &	context ) const

Saves the method to a DOM element and return it.

Parameters

doc	the DOM document
context	the read/write context

Definition at line 103 of file qgsclassificationmethod.cpp.

◆ setLabelFormat()

void QgsClassificationMethod::setLabelFormat ( const QString & format )

inline

Defines the format of the labels for the classes, using %1 and %2 for the bounds.

Definition at line 220 of file qgsclassificationmethod.h.

◆ setLabelPrecision()

void QgsClassificationMethod::setLabelPrecision ( int labelPrecision )

Defines the precision for the formatting of the labels.

Definition at line 144 of file qgsclassificationmethod.cpp.

◆ setLabelTrimTrailingZeroes()

void QgsClassificationMethod::setLabelTrimTrailingZeroes ( bool trimTrailingZeroes )

inline

Defines if the trailing 0 are trimmed in the label.

Definition at line 228 of file qgsclassificationmethod.h.

◆ setParameterValues()

void QgsClassificationMethod::setParameterValues ( const QVariantMap & values )

Defines the values of the additional parameters.

Since: QGIS 3.12

Definition at line 199 of file qgsclassificationmethod.cpp.

◆ setSymmetricMode()

void QgsClassificationMethod::setSymmetricMode	(	bool	enabled,
		double	symmetryPoint = 0,
		bool	symmetryAstride = false )

Defines if the symmetric mode is enables and configures its parameters.

If the symmetric mode is not available in the current implementation, calling this method has no effect.

Parameters

enabled	if the symmetric mode is enabled
symmetryPoint	the value of the symmetry point
symmetryAstride	if `true`, it will remove the symmetry point break so that the 2 classes form only one

Definition at line 137 of file qgsclassificationmethod.cpp.

◆ symmetricModeAvailable()

bool QgsClassificationMethod::symmetricModeAvailable ( ) const

inline

Returns if the method supports symmetric calculation.

Definition at line 189 of file qgsclassificationmethod.h.

◆ symmetricModeEnabled()

bool QgsClassificationMethod::symmetricModeEnabled ( ) const

inline

Returns if the symmetric mode is enabled.

Definition at line 194 of file qgsclassificationmethod.h.

◆ symmetryAstride()

bool QgsClassificationMethod::symmetryAstride ( ) const

inline

Returns if the symmetric mode is astride if true, it will remove the symmetry point break so that the 2 classes form only one.

Definition at line 205 of file qgsclassificationmethod.h.

◆ symmetryPoint()

double QgsClassificationMethod::symmetryPoint ( ) const

inline

Returns the symmetry point for symmetric mode.

Definition at line 199 of file qgsclassificationmethod.h.

◆ valuesRequired()

virtual bool QgsClassificationMethod::valuesRequired ( ) const

inlinevirtual

Returns if the method requires values to calculate the classes If not, bounds are sufficient.

Reimplemented in QgsClassificationCustom, QgsClassificationEqualInterval, QgsClassificationFixedInterval, QgsClassificationLogarithmic, and QgsClassificationPrettyBreaks.

Definition at line 177 of file qgsclassificationmethod.h.

◆ writeXml()

virtual void QgsClassificationMethod::writeXml	(	QDomElement &	element,
		const QgsReadWriteContext &	context ) const

inlinevirtual

Writes extra information about the method.

Reimplemented in QgsClassificationStandardDeviation.

Definition at line 169 of file qgsclassificationmethod.h.

Member Data Documentation

◆ MAX_PRECISION

const int QgsClassificationMethod::MAX_PRECISION = 15

static

Definition at line 326 of file qgsclassificationmethod.h.

◆ MIN_PRECISION

const int QgsClassificationMethod::MIN_PRECISION = -6

static

Definition at line 327 of file qgsclassificationmethod.h.

The documentation for this class was generated from the following files:

/build/qgis-3.99.0+git20251205+26c88405ac0+99sid/src/core/classification/qgsclassificationmethod.h
/build/qgis-3.99.0+git20251205+26c88405ac0+99sid/src/core/classification/qgsclassificationmethod.cpp

Public Types

Public Member Functions

Static Public Member Functions

Static Public Attributes

Protected Member Functions

Detailed Description

Member Typedef Documentation

◆ MethodProperties

Member Enumeration Documentation

◆ ClassPosition

◆ MethodProperty

Constructor & Destructor Documentation

◆ QgsClassificationMethod()

◆ ~QgsClassificationMethod()

Member Function Documentation

◆ addParameter()

◆ classes() [1/3]

◆ classes() [2/3]

◆ classes() [3/3]

◆ classesV2()

◆ clone()

◆ codeComplexity()

◆ copyBase()

◆ create()

◆ flags()

◆ formatNumber()

◆ icon()

◆ id()

◆ labelFormat()

◆ labelForRange() [1/2]

◆ labelForRange() [2/2]

◆ labelPrecision()

◆ labelTrimTrailingZeroes()

◆ makeBreaksSymmetric()

◆ name()

◆ parameterDefinition()

◆ parameterDefinitions()

◆ parameterValues()

◆ rangesToBreaks()

◆ readXml()

◆ save()

◆ setLabelFormat()

◆ setLabelPrecision()

◆ setLabelTrimTrailingZeroes()

◆ setParameterValues()

◆ setSymmetricMode()

◆ symmetricModeAvailable()

◆ symmetricModeEnabled()

◆ symmetryAstride()

◆ symmetryPoint()

◆ valuesRequired()

◆ writeXml()

Member Data Documentation

◆ MAX_PRECISION

◆ MIN_PRECISION