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Version: Python

head_by

head_by returns the first n rows for each group.

Syntax​

table.head_by(n: int, by: Union[str, list[str]]) -> Table

Parameters​

ParameterTypeDescription
nint

The number of rows to return for each group.

by optionalUnion[str, list[str]]

The column(s) by which to group data.

  • ["X"] will output the entire first n row(s) of each group in column X.
  • ["X", "Y"] will output the entire first n row(s) of each group designated from the X and Y columns.

Returns​

A new table containing the first n rows for each group.

Examples​

In this example, head_by returns the first 2 rows, as grouped by X.

from deephaven import new_table
from deephaven.column import string_col, int_col

source = new_table(
    [
        string_col("X", ["A", "B", "A", "A", "B", "A", "B", "B", "B"]),
        string_col("Y", ["M", "M", "M", "N", "M", "M", "M", "M", "M"]),
        int_col("Number", [55, 76, 20, 130, 230, 50, 73, 137, 214]),
    ]
)

result = source.head_by(2, by=["X"])

In this example, head_by returns the first 2 rows, as grouped by X and Y.

from deephaven import new_table
from deephaven.column import string_col, int_col

source = new_table(
    [
        string_col("X", ["A", "B", "A", "A", "B", "A", "B", "B", "B"]),
        string_col("Y", ["M", "M", "M", "N", "M", "M", "M", "M", "M"]),
        int_col("Number", [55, 76, 20, 130, 230, 50, 73, 137, 214]),
    ]
)

result = source.head_by(2, by=["X", "Y"])