Class: QgsAggregateCalculator¶
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class
qgis.core.
QgsAggregateCalculator
(layer: QgsVectorLayer)¶ Bases:
sip.wrapper
Constructor for QgsAggregateCalculator.
- Parameters
layer – vector layer to calculate aggregate from
QgsAggregateCalculator(QgsAggregateCalculator)
Utility class for calculating aggregates for a field (or expression) over the features from a vector layer. It is recommended that QgsVectorLayer.aggregate() is used rather then directly using this class, as the QgsVectorLayer method can handle delegating aggregate calculation to a data provider for remote calculation.
New in version 2.16: Enums
Methods
Structured information for available aggregates.
Calculates the value of an aggregate.
Returns the delimiter used for joining values with the StringConcatenate aggregate.
Returns the filter which limits the features used during the aggregate calculation.
Returns the associated vector layer.
Sets the delimiter to use for joining values with the StringConcatenate aggregate.
Sets a filter to limit the features used during the aggregate calculation.
Sets a filter to limit the features used during the aggregate calculation.
Sets all aggregate parameters from a parameter bundle.
Converts a string to a aggregate type.
Signals
Attributes
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class
Aggregate
¶ Bases:
int
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class
AggregateInfo
¶ Bases:
sip.wrapper
QgsAggregateCalculator.AggregateInfo(QgsAggregateCalculator.AggregateInfo)
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function
¶
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name
¶
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supportedTypes
¶
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class
AggregateParameters
¶ Bases:
sip.wrapper
QgsAggregateCalculator.AggregateParameters(QgsAggregateCalculator.AggregateParameters)
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delimiter
¶
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filter
¶
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orderBy
¶
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ArrayAggregate
= 20¶
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Count
= 0¶
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CountDistinct
= 1¶
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CountMissing
= 2¶
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FirstQuartile
= 13¶
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GeometryCollect
= 19¶
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InterQuartileRange
= 15¶
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Majority
= 12¶
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Max
= 4¶
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Mean
= 6¶
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Median
= 7¶
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Min
= 3¶
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Minority
= 11¶
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Range
= 10¶
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StDev
= 8¶
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StDevSample
= 9¶
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StringConcatenate
= 18¶
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StringConcatenateUnique
= 21¶
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StringMaximumLength
= 17¶
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StringMinimumLength
= 16¶
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Sum
= 5¶
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ThirdQuartile
= 14¶
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aggregates
() → List[QgsAggregateCalculator.AggregateInfo]¶ Structured information for available aggregates.
New in version 3.2.
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calculate
(self, aggregate: QgsAggregateCalculator.Aggregate, fieldOrExpression: str, context: QgsExpressionContext = None) → Tuple[Any, bool]¶ Calculates the value of an aggregate.
- Parameters
aggregate – aggregate to calculate
fieldOrExpression – source field or expression to use as basis for aggregated values. If an expression is used, then the context parameter must be set.
context – expression context for evaluating expressions
ok – if specified, will be set to
True
if aggregate calculation was successful
- Returns
calculated aggregate value
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delimiter
(self) → str¶ Returns the delimiter used for joining values with the StringConcatenate aggregate.
See also
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filter
(self) → str¶ Returns the filter which limits the features used during the aggregate calculation.
See also
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layer
(self) → QgsVectorLayer¶ Returns the associated vector layer.
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setDelimiter
(self, delimiter: str)¶ Sets the delimiter to use for joining values with the StringConcatenate aggregate.
- Parameters
delimiter – string delimiter
See also
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setFidsFilter
(self, fids: object)¶ Sets a filter to limit the features used during the aggregate calculation. If an expression filter is set, it will override this filter.
- Parameters
fids – feature ids for feature filtering, and empty list will return no features.
See also
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setFilter
(self, filterExpression: str)¶ Sets a filter to limit the features used during the aggregate calculation.
- Parameters
filterExpression – expression for filtering features, or empty string to remove filter
See also
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setParameters
(self, parameters: QgsAggregateCalculator.AggregateParameters)¶ Sets all aggregate parameters from a parameter bundle.
- Parameters
parameters – aggregate parameters
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stringToAggregate
(string: str) → Tuple[QgsAggregateCalculator.Aggregate, bool]¶ Converts a string to a aggregate type.
- Parameters
string – string to convert
ok – if specified, will be set to
True
if conversion was successful
- Returns
aggregate type