Delta
Creates a Delta UpdateByOperation for the supplied column names. The Delta operation produces values by computing the difference between the current value and the previous value. By default, null values in the current or previous cell produce null output. This behavior can be changed using DeltaControl.
Syntax
Delta(pairs...)
Delta(control, pairs...)
Parameters
| Parameter | Type | Description |
|---|---|---|
| pairs | String... | The input/output column name pairs. |
| control | DeltaControl | Defines how special cases should behave. See |
Returns
An UpdateByOperation to be used in an updateBy table operation.
Examples
One column, no groups
The following example calculates the delta of the X column, renaming the resultant column to Delta_X. No grouping columns are specified, so the delta is calculated for all rows.
source = emptyTable(10).update("Letter = (i % 2 == 0) ? `A` : `B`", "X = randomInt(0,25)")
result = source.updateBy([Delta("Delta_X = X")])
- source
- result
One Delta column, one grouping column
The following example builds on the previous by specifying Letter as the key column. Thus, the Delta is calculated on a per-letter basis.
source = emptyTable(10).update("Letter = (i % 2 == 0) ? `A` : `B`", "X = randomInt(0,25)")
result = source.updateBy([Delta("Delta_X = X")], "Letter")
- source
- result
Multiple Delta columns, multiple grouping columns
The following example builds on the previous by calculating the Delta of multiple columns with each UpdateByOperation. Also, the groups are defined by unique combinations of letter and boolean in the Letter and Truth columns, respectively.
source = emptyTable(20).update("Letter = (i % 2 == 0) ? `A` : `B`", "Truth = randomBool()", "X = randomInt(0, 25)", "Y = randomInt(0, 25)")
result = source.updateBy([Delta("Delta_X = X", "Delta_Y = Y")], "Letter", "Truth")
- source
- result
Multiple UpdateByOperations, multiple grouping columns
The following example builds on the previous by calculating Delta of the X and Y columns using different Delta UpdateByoperations.
source = emptyTable(20).update("Letter = (i % 2 == 0) ? `A` : `B`", "Truth = randomBool()", "X = randomInt(0, 25)", "Y = randomInt(0, 25)")
DeltaX = Delta("DeltaX = X")
DeltaY = Delta("DeltaY = Y")
result = source.updateBy([DeltaX, DeltaY], "Letter", "Truth")
- source
- result