How to find difference between two rows of data?

[Anonymous]

I have data as shown in a small snippet below. I would like to add a new column that shows the difference from one row to the next. Can anyone show me the DAX code to do this?

[johnt75]

Diff to previous = IF( currentIndex > 0,
var currentIndex = 'Table'[index]
var currentValue = 'Table'[Value]
var prevValue = LOOKUPVALUE( 'Table'[Value], 'Table'[index], currentIndex - 1)
return currentValue - prevValue
)

[Anonymous]

Hi @johnt75 ,

Tried your code but currentIndex on line 1 is greyed out and gives the error "Failed to resolve name 'currentIndex'. Rest of the lines seem to work fine. Any idea how to fix this?

[johnt75 · Accepted solution]

My mistake, I changed my mind about where to put the check for 0 index whilst I was writing it.

Diff to previous = 
var currentIndex = 'Table'[index]
IF( currentIndex > 0,
var currentValue = 'Table'[Value]
var prevValue = LOOKUPVALUE( 'Table'[Value], 'Table'[index], currentIndex - 1)
return currentValue - prevValue
)