GroupByBuilder

Namespace: Polars.CSharp

Unified builder for DataFrame GroupBy operations (Standard, Dynamic, Rolling)

Instance Methods

Agg

Aggregate with specified expressions. Under the hood, this routes through the Lazy engine to maximize performance and optimizations.

public DataFrame Agg(params Expr[] aggs)

Parameters

Name	Type	Description
aggs	Expr[]	Aggregation expressions

Returns: A new aggregated DataFrame

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All

Aggregate all columns into lists.

public DataFrame All()

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Count

Count the number of values in each group.

public DataFrame Count()

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First

Aggregate the first values in the group.

public DataFrame First(bool ignoreNulls = false)

Parameters

Name	Type	Description
ignoreNulls	bool	Ignore null values (default False). If set to True, the first non-null value for each aggregation is returned, otherwise None is returned if no non-null value exists.

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GetEnumerator

Allows iteration over the groups of the group by operation.

public IEnumerator<(object[], DataFrame)> GetEnumerator()

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GetGroups

Allows iteration over the groups of the group by operation.(Strong Typed)

public IEnumerable<(TKey, DataFrame)> GetGroups<TKey>()

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Having

Filter groups with a predicate after aggregation.

public GroupByBuilder Having(Expr predicate)

Parameters

Name	Type	Description
predicate	Expr	-

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Head

public DataFrame Head(int n = 10)

Parameters

Name	Type	Description
n	int	-

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Last

Aggregate the last values in the group.

public DataFrame Last(bool ignoreNulls = false)

Parameters

Name	Type	Description
ignoreNulls	bool	Ignore null values (default False). If set to True, the last non-null value for each aggregation is returned, otherwise None is returned if no non-null value exists.

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Len

Return the number of rows in each group.

public DataFrame Len(string name = "len")

Parameters

Name	Type	Description
name	string	Assign a name to the resulting column; if unset, defaults to “len”.

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Max

Reduce the groups to the maximal value.

public DataFrame Max()

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Mean

Reduce the groups to the mean value.

public DataFrame Mean()

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Median

Reduce the groups to the median value.

public DataFrame Median()

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Min

Reduce the groups to the minimal value.

public DataFrame Min()

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NUnique

Count the unique values per group.

public DataFrame NUnique()

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Quantile

Compute the quantile per group.

public DataFrame Quantile(double quantile, QuantileMethod interpolation = QuantileMethod.Linear)

Parameters

Name	Type	Description
quantile	double	Quantile between 0.0 and 1.0.
interpolation	QuantileMethod	Interpolation method.

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Sum

Reduce the groups to the sum.

public DataFrame Sum()

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Tail

public DataFrame Tail(int n = 10)

Parameters

Name	Type	Description
n	int	-

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