changed(a: ‘a) 🡒 boolean, ordered aggregator
The aggregator returns
true for the first line of each group, and for each line that is different from the previous one. It requires an ordering option, either
table T = with [| as Val |] [| "a" |] // changed = true [| "a" |] [| "b" |] // changed = true [| "b" |] [| "b" |] [| "c" |] // changed = true show table "" a1b6 with T.Val changed(T.Val) scan auto
This aggregator is intended to facilitate skipping unchanged lines while persisting data, like historical prices.
number variant of this aggregator is equivalent to the user-defined process as defined below:
def process changed_bis(next: number) default false with keep prev = 0 changed = prev != next prev = next return argfirst() or changed