MAX difference between current row and previous row as a measure

[music43]

Hi 
I am trying to learn how to DAX and I have been trying to figure this out for the last couple of days, but getting nowhere.

I am trying to subtract the value of the previous row from the of current row (which I appear to have managed) and then get the overall MAX. In the example below returning 15.

My questions are:
1) Is the LOOKUPVALUE the best way to get the prevVal or are there better ways of doing this?
2) How do I then get the MAX?

I tried MAXX around the RETURN formula but wasn't getting anywhere...

Any guidance is appreciated.

Thanks

Oli

[Jihwan_Kim · Accepted solution]

Hi,

I tried to create a sample pbix file like below.

Please check the below picture and the attached pbix file.

Expected result measure: = 
MAXX (
    ADDCOLUMNS (
        FILTER (
            ADDCOLUMNS (
                Data,
                "@prevvalue",
                    CALCULATE (
                        SUM ( Data[Value] ),
                        FILTER ( Data, Data[Index ID] = EARLIER ( Data[Index ID] ) - 1 )
                    )
            ),
            [@prevvalue] <> BLANK ()
        ),
        "@diff", Data[Value] - [@prevvalue]
    ),
    [@diff]
)