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changed

changed, process

def process changed(value: any): boolean

Returns true if the current value is different from the previous value; always returns true for the first element. This process function must be used with either scan or sort ordering option.

value: The value to monitor for changes across consecutive lines.

Examples

Basic usage with sorting

table T = with
  [| as Id, as Category |]
  [| 1,    "A"          |]
  [| 2,    "A"          |]
  [| 3,    "B"          |]
  [| 4,    "B"          |]
  [| 5,    "A"          |]

T.HasChanged = changed(T.Category) scan T.Id

show table "Category changes" with
  T.Id
  T.Category
  T.HasChanged

This produces:

Id	Category	HasChanged
1	A	True
2	A	False
3	B	True
4	B	False
5	A	True

Detecting day changes in a date series

table Sales = with
  [| as Date,            as Amount |]
  [| date(2023, 1, 1),   100       |]
  [| date(2023, 1, 1),   150       |]
  [| date(2023, 1, 2),   200       |]
  [| date(2023, 1, 2),   250       |]
  [| date(2023, 1, 3),   300       |]

Sales.NewDay = changed(Sales.Date) scan Sales.Date

show table "Daily sales breakdown" with
  Sales.Date
  Sales.Amount
  Sales.NewDay

This produces the following table of daily sales:

Date	Amount	NewDay
Jan 1, 2023	100	True
Jan 1, 2023	150	False
Jan 2, 2023	200	True
Jan 2, 2023	250	False
Jan 3, 2023	300	True

Detecting stock level changes by product

table StockLevels = with
  [| as Date,           as Product,   as Stock |]
  [| date(2023, 1, 1),  "Widget A",   120      |]
  [| date(2023, 1, 2),  "Widget A",   85       |]
  [| date(2023, 1, 3),  "Widget A",   85       |]
  [| date(2023, 1, 1),  "Widget B",   50       |]
  [| date(2023, 1, 2),  "Widget B",   50       |]
  [| date(2023, 1, 3),  "Widget B",   75       |]

StockLevels.StockChanged = changed(StockLevels.Stock)
  by StockLevels.Product
  sort StockLevels.Date

show table "Stock Level Changes" with
  StockLevels.Date
  StockLevels.Product
  StockLevels.Stock
  StockLevels.StockChanged

This examples produces the following table of stock level changes:

Date	Product	Stock	StockChanged
Jan 1, 2023	Widget A	120	True
Jan 2, 2023	Widget A	85	True
Jan 3, 2023	Widget A	85	False
Jan 1, 2023	Widget B	50	True
Jan 2, 2023	Widget B	50	False
Jan 3, 2023	Widget B	75	True

Remarks

The changed process function requires a scan/sort option to specify the order in which values will be compared. Without a specified order, your code will not compile.

This process can be used with any data type that supports equality comparison, including numbers, text, dates, and booleans.

Recipes and best practices

Segmenting data by changes: Use changed to identify natural boundaries in sorted data:
Dates.NewMonth = changed(month(Dates.Date)) scan Dates.Date
Counting transitions: Combine with sum to count how many times a value changes:
categoryChanges = sum(if changed(Items.Category) scan Items.Id then 1 else 0)
Track delivery status changes for notifications: Identify when a package’s delivery status changes (e.g., to trigger customer notifications):
DeliveryLog.StatusChanged = changed(DeliveryLog.Status) by DeliveryLog.TrackingNumber scan DeliveryLog.Timestamp