How to generate a Yearly report based on a calculation at the Month level

Question

Have the need to create a report as follows. Any ideas on how this can be accomplished in OBI is appreciated. I have already tried different ways but non worked for me.
The data is stored in a table at day level as follows:
Day Amount_A Amouont_B
1/1/2008     100     100
1/15/2008     200     100
2/1/2008     100     400
2/15/2008     300     200
1/1/2009     100     300
1/15/2009     100     200
2/1/2009     200     100
2/15/2009     400     300
The report should be displayed at Year level. Amount_A is just the summation of Amount_A from the table at daily level rolled up to the Year level in the Time dimension. The same thing for Amount_B.
The formula for Absolute_Error is Absolute(Amount_A - Amount_B). But the problem is that it has to be calculated at the Month level instead of Day Level. So following is the logic for Absolute_Error:
Month     Amount_A Amount_B     Absolute_Error
Jan-2008     300     200     100
Feb-2008     400     600     200
Jan-2009     200     500     300
Feb-2009     600     400     200
The report should be displayed as follows:
Year Amount_A Amount_B     Absolute_Error
2008     700     800     300
2009     800     900     500
Note that the calculation of Absolute_Error results in a different value if it is calculated at the Month level and summed up to Year than if it were calculated at the Day level and then summed up to Year. It is required to be based on Month level for this report.
Is there a way to do this without having to build an aggregated fact table at the Month level?

Answer 1

Hi.
Do this:
1. Create Amount_A and Amount_B in BMM without SUM as default aggregation rule.
2. Now, just go to Answers and make report with three columns:
YEAR -- EXPRESSION 1 -- EXPRESSION 2
EXPRESSION 1 is:
sum(Amount_A) - sum(Amount_B)
EXPRESSION 2 is:
sum
abs
sum(Amount_A by MONTH)
sum(Amount_B by MONTH)
My example in Answers:
TIMES.CALENDAR_YEAR
sum(SALES.QUANTITY_SOLD_NORMAL) - sum(SALES.AMOUNT_SOLD_NORMAL)
sum( abs(sum(SALES.QUANTITY_SOLD_NORMAL by TIMES.CALENDAR_MONTH_DESC) - sum(SALES.AMOUNT_SOLD_NORMAL by TIMES.CALENDAR_MONTH_DESC) ) )
This will first summarize amount A and amount B on a month level and then do a difference, after that ABS and then sum on the year level.
This is workaround to avoid larger RPD changes.
Regards,
Goran O
http://108obiee.blogspot.com/