LazyGroupBy

Namespace: Polars.CSharp

A unified builder for Standard, Dynamic, and Rolling GroupBy operations.

Instance Methods

Agg

Apply aggregations to the group.

public LazyFrame Agg(params Expr[] aggs)

Parameters

Name	Type	Description
aggs	Expr[]	-

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All

Aggregate all columns into lists.

public LazyFrame All()

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Count

Count the number of values in each group.

public LazyFrame Count()

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First

Aggregate the first values in the group.

public LazyFrame 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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Having

Filter groups with a list of predicates after aggregation. Using this method is equivalent to adding the predicates to the aggregation and filtering afterwards.

public LazyGroupBy Having(Expr predicate)

Parameters

Name	Type	Description
predicate	Expr	Expressions that evaluate to a boolean value for each group. Typically, this requires the use of an aggregation function.

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Head

Get the first n rows of each group.

public LazyFrame Head(int n = 10)

Parameters

Name	Type	Description
n	int	-

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Last

Aggregate the last values in the group.

public LazyFrame 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 LazyFrame 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 LazyFrame Max()

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Mean

Reduce the groups to the mean value.

public LazyFrame Mean()

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Median

Reduce the groups to the median value.

public LazyFrame Median()

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Min

Reduce the groups to the minimal value.

public LazyFrame Min()

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NUnique

Count the unique values per group.

public LazyFrame NUnique()

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Quantile

Compute the quantile per group.

public LazyFrame 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 LazyFrame Sum()

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Tail

Get the last n rows of each group.

public LazyFrame Tail(int n = 10)

Parameters

Name	Type	Description
n	int	-

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