AggFormula
AggFormula returns an aggregator that computes a user-defined formula aggregation across specified columns. This allows you to apply custom formulas to groups of rows, leveraging built-in, mathematical, or user-defined functions.
Syntax
AggFormula(formula, paramToken, columnNames...)
Parameters
| Parameter | Type | Description |
|---|---|---|
| formula | String | The user-defined formula to apply to each group. This formula can contain:
If Key column(s) can be used as input to the formula. When this happens, key values are treated as scalars. |
| paramToken | String | The parameter name within the formula. If |
| columnNames | String... | The source column(s) for the calculations.
|
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 a name conflict error.
Returns
An aggregator that computes a user-defined formula within an aggregation group, for each input column.
Examples
The following example uses AggFormula to calculate several formula aggregations by the Letter column. Since paramToken is null, the formulas are applied to any column or literal value present in the formula. The specified formulas operate on zero, one, two, and three different columns at a time.
source = emptyTable(20).update("X = i", "Y = 2 * i", "Z = 3 * i", "Letter = (X % 2 == 0) ? `A` : `B`")
result = source.aggBy([
AggFormula("OutA = sqrt(5.0)"),
AggFormula("OutB = min(X)"),
AggFormula("OutC = min(X) + max(Y)"),
AggFormula("OutD = sum(X + Y + Z)"),
], "Letter")
The following example uses AggFormula to calculate the aggregate minimum across several columns by the Letter column. Since paramToken is not null, the formula is applied to the specified paramToken.
import static io.deephaven.api.agg.Aggregation.AggFormula
source = emptyTable(20).update("X = i", "Y = 2 * i", "Z = 3 * i", "Letter = (X % 2 == 0) ? `A` : `B`")
result = source.aggBy([AggFormula("min(each)", "each", "MinX = X", "MinY = Y", "MinZ = Z")], "Letter")
In this example, AggFormula is used to calculate the aggregated average across several column by the Letter and Color columns. Since paramToken is not null, the formula is applied to the specified paramToken.
import static io.deephaven.api.agg.Aggregation.AggFormula
colors = ["Red", "Green", "Blue"]
source = emptyTable(40).update("X = 0.1 * i", "Y1 = Math.pow(X, 2)", "Y2 = Math.sin(X)", "Y3 = Math.cos(X)", "Letter = (i % 2 == 0) ? `A` : `B`", "Color = (String)colors[i % 3]")
myAgg = [AggFormula("avg(k)", "k", "AvgY1 = Y1", "AvgY2 = Y2", "AvgY3 = Y3")]
result = source.aggBy(myAgg, "Letter", "Color")
In this example, AggFormula is used to calculate the aggregate sum of squares across each of the X, Y and Z columns by the Letter column. Since paramToken is not null, the formula is applied to the specified paramToken.
import static io.deephaven.api.agg.Aggregation.AggFormula
source = emptyTable(20).update("X = i", "Y = 2 * i", "Z = 3 * i", "Letter = (X % 2 == 0) ? `A` : `B`")
myAgg = [AggFormula("sum(each * each)", "each", "SumSqrX = X", "SumSqrY = Y", "SumSqrZ = Z")]
result = source.aggBy(myAgg, "Letter")
In this example, AggFormula calls a user-defined closure to compute the range of the X, Y, and Z columns by the Letter column. Since paramToken is not null, the formula is applied to the specified paramToken.
Note
The output of an AggFormula is of type java.lang.Object unless an explicit typecast is made in the formula string.
import static io.deephaven.api.agg.Aggregation.AggFormula
source = emptyTable(20).update("X = i", "Y = 2 * i", "Z = 3 * i", "Letter = (X % 2 == 0) ? `A` : `B`")
rangeX = {x -> x.max() - x.min()}
myAgg = [AggFormula("(int)rangeX(each)", "each", "RangeX = X", "RangeY = Y", "RangeZ = Z")]
result = source.aggBy(myAgg, "Letter")