AggFirst

AggFirst returns an aggregator that computes the first value, within an aggregation group, for each input column.

Syntax

AggFirst(pairs...)

Parameters

ParameterTypeDescription
pairsString...

The source columns for the calculations.

  • "X" will output the first value in the X column for each group.
  • "Y = X" will output the first value in the X column for each group and rename it to Y.
  • "X, A = B" will output the first value in the X column for each group and the first value in the B column while renaming it to A.

Caution

If an aggregation does not rename the resulting column, the aggregation column will appear in the output table, not the input column. If multiple aggregations on the same column do not rename the resulting columns, an error will result, because the aggregations are trying to create multiple columns with the same name. For example, in table.aggBy([agg.AggSum(“X”), agg.AggAvg(“X”)]), both the sum and the average aggregators produce column X, which results in an error.

Returns

An aggregator that computes the first value, within an aggregation group, for each input column.

Examples

In this example, AggFirst returns the first Y value as grouped by X.

import static io.deephaven.api.agg.Aggregation.AggFirst

source = newTable(
    stringCol("X", "A", "B", "A", "C", "B", "A", "B", "B", "C"),
    stringCol("Y", "M", "N", "O", "N", "P", "M", "O", "P", "M"),
    intCol("Number", 55, 76, 20, 130, 230, 50, 73, 137, 214),
)

result = source.aggBy([AggFirst("Y")], "X")

In this example, AggFirst returns the first Y value (renamed to Z), as grouped by X.

import static io.deephaven.api.agg.Aggregation.AggFirst

source = newTable(
    stringCol("X", "A", "B", "A", "C", "B", "A", "B", "B", "C"),
    stringCol("Y", "M", "N", "O", "N", "P", "M", "O", "P", "M"),
    intCol("Number", 55, 76, 20, 130, 230, 50, 73, 137, 214),
)

result = source.aggBy([AggFirst("Z = Y")], "X")

In this example, AggFirst returns the first Y string and first Number integer, as grouped by X.

import static io.deephaven.api.agg.Aggregation.AggFirst

source = newTable(
    stringCol("X", "A", "B", "A", "C", "B", "A", "B", "B", "C"),
    stringCol("Y", "M", "N", "O", "N", "P", "M", "O", "P", "M"),
    intCol("Number", 55, 76, 20, 130, 230, 50, 73, 137, 214),
)

result = source.aggBy([AggFirst("Y", "Number")], "X")

In this example, AggFirst returns the first Number integer, as grouped by X and Y.

import static io.deephaven.api.agg.Aggregation.AggFirst

source = newTable(
    stringCol("X", "A", "B", "A", "C", "B", "A", "B", "B", "C"),
    stringCol("Y", "M", "P", "O", "N", "P", "M", "O", "P", "N"),
    intCol("Number", 55, 76, 20, 130, 230, 50, 73, 137, 214),
)

result = source.aggBy([AggFirst("Number")], "X", "Y")

In this example, AggFirst returns the first Number integer, and AggLast returns the last Number integer, as grouped by X.

import static io.deephaven.api.agg.Aggregation.AggFirst
import static io.deephaven.api.agg.Aggregation.AggLast

source = newTable(
    stringCol("X", "A", "B", "A", "C", "B", "A", "B", "B", "C"),
    stringCol("Y", "M", "P", "O", "N", "P", "M", "O", "P", "N"),
    intCol("Number", 55, 76, 20, 130, 230, 50, 73, 137, 214),
)

result = source.aggBy([AggFirst("FirstNumber = Number"),AggLast("LastNumber = Number")], "X")