How do I use the DAX function ParallelPeriod - excel

Question

The ParaellePeriod function allows for the comparison of values between points in time (how do sales compare to a year ago). I'm doing something wrong in my use of it, but have no idea what that thing may be.
Set up
I created a bog simple PowerPivot SQL Server 2008+ source query and named it Source. The query generates 168 rows: 6 IDs (100-600) and 28 dates (first of a month from Jan 2010 to Apr 2012) all cross applied together.
; WITH SRC (groupKey, eventDate, value) AS
(
SELECT G.groupKey, D.eventDate, CAST(rand(G.groupKey * year(D.eventDate) * month(D.eventDate)) * 100 AS int)
FROM
(
SELECT 100
UNION ALL SELECT 200
UNION ALL SELECT 300
UNION ALL SELECT 400
UNION ALL SELECT 500
UNION ALL SELECT 600
) G (groupKey)
CROSS APPLY
(
SELECT CAST('2010-01-01' AS date)
UNION ALL SELECT CAST('2010-02-01' AS date)
UNION ALL SELECT CAST('2010-03-01' AS date)
UNION ALL SELECT CAST('2010-04-01' AS date)
UNION ALL SELECT CAST('2010-05-01' AS date)
UNION ALL SELECT CAST('2010-06-01' AS date)
UNION ALL SELECT CAST('2010-07-01' AS date)
UNION ALL SELECT CAST('2010-08-01' AS date)
UNION ALL SELECT CAST('2010-09-01' AS date)
UNION ALL SELECT CAST('2010-10-01' AS date)
UNION ALL SELECT CAST('2010-11-01' AS date)
UNION ALL SELECT CAST('2010-12-01' AS date)
UNION ALL SELECT CAST('2011-01-01' AS date)
UNION ALL SELECT CAST('2011-02-01' AS date)
UNION ALL SELECT CAST('2011-03-01' AS date)
UNION ALL SELECT CAST('2011-04-01' AS date)
UNION ALL SELECT CAST('2011-05-01' AS date)
UNION ALL SELECT CAST('2011-06-01' AS date)
UNION ALL SELECT CAST('2011-07-01' AS date)
UNION ALL SELECT CAST('2011-08-01' AS date)
UNION ALL SELECT CAST('2011-09-01' AS date)
UNION ALL SELECT CAST('2011-10-01' AS date)
UNION ALL SELECT CAST('2011-11-01' AS date)
UNION ALL SELECT CAST('2011-12-01' AS date)
UNION ALL SELECT CAST('2012-01-01' AS date)
UNION ALL SELECT CAST('2012-02-01' AS date)
UNION ALL SELECT CAST('2012-03-01' AS date)
UNION ALL SELECT CAST('2012-04-01' AS date)
) D (eventDate)
)
SELECT
*
FROM
SRC;
I added a derived column in PowerPivot using a formula I lifted from MSDN
=CALCULATE(SUM(Source[value]), PARALLELPERIOD(Source[eventDate], -1, year))
There are no errors displayed but there's never any calculated data. I've tried different intervals (-1, +1) and periods (year, month) but to no avail.
The only thing I could observe that was different between my demo and the MSDN was theirs had a separate dimension defined for the date. Easy enough to rectify so I created a Dates query with the following. This query generates a row for all the days between 2010-01-01 and 2012-06-01 (1096 rows)
DECLARE
#start int = 20100101
, #stop int = 20120601;
WITH L0 AS
(
SELECT
0 AS C
UNION ALL
SELECT
0
)
, L1 AS
(
SELECT
0 AS c
FROM
L0 AS A
CROSS JOIN L0 AS B
)
, L2 AS
(
SELECT
0 AS c
FROM
L1 AS A
CROSS JOIN L1 AS B
)
, L3 AS
(
SELECT
0 AS c
FROM
L2 AS A
CROSS JOIN L2 AS B
)
, L4 AS
(
SELECT
0 AS c
FROM
L3 AS A
CROSS JOIN L3 AS B
)
, L5 AS
(
SELECT
0 AS c
FROM
L4 AS A
CROSS JOIN L4 AS B
)
, NUMS AS
(
SELECT
ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) AS number
FROM
L5
)
, YEARS AS
(
SELECT
Y.number
FROM
NUMS Y
WHERE
Y.number BETWEEN #start / 10000 AND #stop / 10000
)
, MONTHS AS
(
SELECT
Y.number
FROM
NUMS Y
WHERE
Y.number BETWEEN 1 and 12
)
, DAYS AS
(
SELECT
Y.number
FROM
NUMS Y
WHERE
Y.number BETWEEN 1 and 31
)
, CANDIDATES_0 AS
(
SELECT
Y.number * 10000 + M.number * 100 + D.number AS SurrogateKey
, CAST(Y.number * 10000 + M.number * 100 + D.number AS char(8)) AS DateValue
FROM
YEARS Y
CROSS APPLY
MONTHS M
CROSS APPLY
DAYS D
)
, HC AS
(
SELECT
Y.number * 10000 + M.number * 100 + D.number AS SurrogateKey
, CAST(Y.number * 10000 + M.number * 100 + D.number AS char(8)) AS DateValue
FROM
YEARS Y
CROSS APPLY
MONTHS M
CROSS APPLY
DAYS D
WHERE
D.number < 31
AND M.number IN (4,6,9,11)
UNION ALL
SELECT
Y.number * 10000 + M.number * 100 + D.number AS SurrogateKey
, CAST(Y.number * 10000 + M.number * 100 + D.number AS char(8)) AS DateValue
FROM
YEARS Y
CROSS APPLY
MONTHS M
CROSS APPLY
DAYS D
WHERE
D.number < 32
AND M.number IN (1,3,5,7,8,10,12)
UNION ALL
SELECT
Y.number * 10000 + M.number * 100 + D.number AS SurrogateKey
, CAST(Y.number * 10000 + M.number * 100 + D.number AS char(8)) AS DateValue
FROM
YEARS Y
CROSS APPLY
MONTHS M
CROSS APPLY
DAYS D
WHERE
D.number < 29
AND M.number = 2
AND
(
Y.number % 4 > 0
OR Y.number % 100 = 0 AND Y.number % 400 > 0
)
UNION ALL
SELECT
Y.number * 10000 + M.number * 100 + D.number AS SurrogateKey
, CAST(Y.number * 10000 + M.number * 100 + D.number AS char(8)) AS DateValue
FROM
YEARS Y
CROSS APPLY
MONTHS M
CROSS APPLY
DAYS D
WHERE
D.number < 30
AND M.number = 2
AND
(
Y.number % 4 = 0
OR Y.number % 100 = 0 AND Y.number % 400 = 0
)
)
, CANDIDATES AS
(
SELECT
C.SurrogateKey
, CAST(C.DateValue as date) As DateValue
FROM
HC C
WHERE
ISDATE(c.DateValue) = 1
)
, PARTS
(
DateKey
, FullDateAlternateKey
, DayNumberOfWeek
, EnglishDayNameOfWeek
, DayNumberOfMonth
, DayNumberOfYear
, WeekNumberOfYear
, EnglishMonthName
, MonthNumberOfYear
, CalendarQuarter
, CalendarYear
, CalendarSemester
--,FiscalQuarter
--,FiscalYear
--,FiscalSemester
) AS
(
SELECT
CAST(C.SurrogateKey AS int)
, C.DateValue
, DATEPART(WEEKDAY, C.DateValue)
, DATENAME(WEEKDAY, C.DateValue)
, DATEPART(DAY, C.DateValue)
, DATEPART(DAYOFYEAR, C.DateValue)
, DATEPART(WEEK, C.DateValue)
, DATENAME(MONTH, C.DateValue)
, DATEPART(MONTH, C.DateValue)
, DATEPART(QUARTER, C.DateValue)
, DATEPART(YEAR, C.DateValue)
, DATEPART(WEEK, C.DateValue)
FROM
CANDIDATES C
WHERE
C.DateValue IS NOT NULL
)
SELECT
P.*
FROM
--HC P
PARTS P
ORDER BY 1;
With data generated, I created a relationship between the Source and Dates and tried this formula with no luck either
=CALCULATE(SUM(Source[value]), PARALLELPERIOD(Dates[FullDateAlternateKey], -1, year))
The PowerPivot designer looks like
Any thoughts on what I'm doing wrong?
References
PARALLELPERIOD Function
PowerPivot DAX PARALLELPERIOD vs DATEADD

Answer 1

The DAX expression you used in the derived column should be a measure and defined in the calculation area...
MeasurePriorPeriodValue := CALCULATE(SUM(Source[value]), PARALLELPERIOD(Source[eventDate], -1, year))
...as long as the column you use in the parallelperiod function is configured as a date datatype, it should still work. Having the date table separated from the rest is "best practice" but not required...because it allows you to ensure that there are no gaps (which can cause problems with some DAX Time-Intelligence functions) and things like that.