month

month, data type

The month is a primitive data type, representing months as the combination of a year and a month number within that year, such as 2001-01 (the earliest month representable in Envision) or 2020-10.

read "/Promo.ion" as Promotions with 
  StartWeek : month
  EndWeek : month

Date arithmetic is supported by the month type: monthA + 1 is the month right after monthA, and monthA - monthB is the number of months between monthA and monthB.

month(y: number, m: number) 🡒 month, const pure function

Returns the month number m in year y ; will raise an error if the combination is incorrect.

show scalar "" with 
  month(2020, 10) // 2020-10

month(d: date) 🡒 month, const pure function

Returns the month associated to the specified date.

show summary "" a1a3 with
  month(date(2019, 12, 28))
  month(date(2019, 12, 30))
  month(date(2020, 1, 1))

Month, special calendar table

The table Month is a special calendar table. This table can only be created with expect [date] in a read block, or by an unfiltering statement with span date =. When introduced, the Month table always has month as its primary dimension (of type month too).

With span:

span date = [date(2024, 1, 1) .. date(2024, 4, 28)]
  // 2-space of indent, we are within the 'span' block
  Month.X = random.uniform(1 into Month, 10 into Month)
  show linechart "Monthly" with Month.X

Or alternatively:

keep span date = [date(2024, 1, 1) .. date(2024, 2, 28)]
// no indent, as 'keep' is used
Month.X = random.uniform(1 into Month, 10 into Month)
show linechart "Monthly" with Month.X

A read block can also be used to introduce the Week table:

read "/sales.csv" as Sales expect [date] with // implicitely creates 'Month'
  "DateOfSales" as date : date // re-map the column originally named 'DateOfSales' to 'date'
  Qty : number

Month.Qty = sum(Sales.Qty) // 'Sales' is downstream of 'Month'
show linechart "Monthly" with Month.Qty

The Month table cannot be created via the usual means, such as table comprehensions for example.

month, primary dimension

The primary dimension of the table Month is named month, and it is of type month.

span date = [date(2024, 1, 1) .. date(2024, 5, 28)]
  // 2-space ident, we are within the 'span' block
  Month.X = random.poisson(5 into Month) // 5 is the mean, broadcast into 'Month'
  myMonth = month(2024, 2) // February of 2024
  show scalar "X in February" with Month.X[myMonth] // look-up on the primary dimension of 'Month'

If a table has date as a primary or secondary dimensions, it automatically receives month as a secondary dimension as well.