Class: QgsAggregateCalculator¶
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class
qgis.core.
QgsAggregateCalculator
(layer: QgsVectorLayer)¶ Bases:
sip.wrapper
Constructor for QgsAggregateCalculator.
- Parameters
layer (QgsVectorLayer) – 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.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 all aggregate parameters from a parameter bundle.
Converts a string to a aggregate type.
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
¶
-
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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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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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
() → object¶ Structured information for available aggregates.
New in version 3.2.
- Return type
object
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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 (QgsAggregateCalculator.Aggregate) – aggregate to calculate
fieldOrExpression (str) – source field or expression to use as basis for aggregated values. If an expression is used, then the context parameter must be set.
context (
QgsExpressionContext
= None) – expression context for evaluating expressionsok – if specified, will be set to true if aggregate calculation was successful
- Return type
Tuple[Any, bool]
- Returns
calculated aggregate value
-
delimiter
(self) → str¶ Returns the delimiter used for joining values with the StringConcatenate aggregate.
See also
- Return type
str
-
filter
(self) → str¶ Returns the filter which limits the features used during the aggregate calculation.
See also
- Return type
str
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layer
(self) → QgsVectorLayer¶ Returns the associated vector layer.
- Return type
-
setDelimiter
(self, delimiter: str)¶ Sets the delimiter to use for joining values with the StringConcatenate aggregate.
- Parameters
delimiter (str) – string delimiter
See also
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setFilter
(self, filterExpression: str)¶ Sets a filter to limit the features used during the aggregate calculation.
- Parameters
filterExpression (str) – expression for filtering features, or empty string to remove filter
See also
-
setParameters
(self, parameters: QgsAggregateCalculator.AggregateParameters)¶ Sets all aggregate parameters from a parameter bundle.
- Parameters
parameters (QgsAggregateCalculator.AggregateParameters) – aggregate parameters
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stringToAggregate
(string: str) → Tuple[QgsAggregateCalculator.Aggregate, bool]¶ Converts a string to a aggregate type.
- Parameters
string (str) – string to convert
ok – if specified, will be set to true if conversion was successful
- Return type
Tuple[QgsAggregateCalculator.Aggregate, bool]
- Returns
aggregate type