how to subtract adjacent columns in an ssrs matrix - sql-server

Question

I have an ssrs matrix which looks like the one below :
Month(Columns)
Product(Rows) Sales(Data)
The output looks something like this :
June July August Sept Oct
ABC 34 34 23 22 67
DEF 33 21 32 22 14
I want an output that looks like this :
June July June-July Aug July-Aug Sept Aug-Sept Oct Sept-Oct
ABC 34 34 0 23 11 22 1 67 45
DEF 33 21 12 32 11 22 10 14 8
I tried doing something like this :
Month(Columns) Change
Product(Rows) Sales(Data) Expression
The expression looks something like this :
=Sum(IIF(Fields!MONTH.Value=Fields!MONTH.Value,Fields!Products.Value,Nothing))-
Sum(IIF(Fields!MONTH.Value=Fields!MONTH.Value - 1,Fields!Products.Value,Nothing))
But it doesnt work . I want to see the output as shown above . Please let me know.
Hey Sam ,
With the solution you mentioned :
I see an output like this :
June Garbage July July-June Aug Aug-Jul
ABC 34 xx 34 0 23 11
DEF 33 xx 21 12 32 11
Is there a way we can remove the column with the garbage values ?
Hey Sam , I tried your code. Now I have a big white space all along the column. Is there a way I can hide the wide space too ?

Answer 1

If you are grouping your columns by month then you don't need to use the SumIif
You can use a expression such as =Sum(Fields!Products.Value) to get the sum of all products in that particular month. If you want to see the difference between the current month and the previous month then if you enter the below expression in a cell within the month column group...
=Iif(Previous(Fields!MONTH.Value) = Nothing, 0,
Sum(Fields!Products.Value) - Previous(Sum(Fields!Products.Value)))
You need the null check in this instance as the first month will return nothing for previous.
If you have overlapping row and column row groups (which I believe you do) then you won't be able to use Previous as it isn't supported :-(
I think that the only solution is to use some custom code.
There is a link here
Public Shared previous as Integer
Public Shared current as Integer
Public Shared Function GetCurrent(Item as Integer) as Integer
previous=current
current=Item
return current
End Function
Public Shared Function GetPrevious()
return previous
End Function
Then your usage would be something like
=Code.GetCurrent(Sum(Fields!Products.Value)) - Code.GetPrevious()

Answer 2

I found a way to calculate the differences between Matrix columns using the 'previous' function by adding the column grouping name.
=Previous(Sum(Fields!AMOUNT.Value),"PeriodGroupName")
Look here for a little more detail.
http://www.tricks-and-tips.nl/tips-and-tricks/sql/ssrs/ssrs-matrix-compare-column-values
And here for the documentation.
https://learn.microsoft.com/en-us/previous-versions/sql/sql-server-2008-r2/ms156372(v=sql.105)