Subtracting Not Working as Expected

[Anonymous]

Hello -

I am working on subtracting Current Data with Past Data using a unique ID to find the last historic value for each unique item. I have successfully calculated the previous value by using the following DAX function:

Previous Data = 
'Table'[Current Data]
    - MAXX(
        FILTER('Table',
            'Table'[Index]
            = EARLIER('Table'[Index]) - 1
            && 'Table'[UID] = EARLIEST('Table'[UID])
        ),
        'Table'[Current Data]
    )

Now that I have this value, I want to subract the each individual row from 'Table' [Current Data] from 'Table' [Previous Data] to get a delta/change value for each row. I used the following as an example:

Delta = 'Table'[Current Data] - 'Table'[Previous Data]

However, when using the above "Delta" calculation all of the values result as "0", and I cannot understand why this is happening.

Below is an example of what I would expect to happen with the delta calculation:

UID	Date	Current Data	Previous Data	Delta
1	2/3/21	5747	8532	(2785)
2	2/3/21	4672	2134	2538
1	1/5/21	8532	8532	0
3	1/3/21	9419	7128	2291
2	1/6/21	2134	9024	(6890)
2	1/2/21	9024	9024	0
3	12/4/20	7128	7128	0

Thank you in advance for any assistance!

[Anonymous]

This seems to have worked perfectly! Thank you!

[amitchandak · Accepted solution]

@Anonymous ,a new column, you can use index in place of date

Diff Previous Data =
var _max = maxx(filter( 'Table','Table'[UID] = EARLIEST('Table'[UID]) , 'Table'[Date] < EARLIER('Table'[Date])),[Date])
return
if(isblank(_max) , 0 , [Current Data] -maxx(filter( 'Table','Table'[UID] = EARLIEST('Table'[UID]) , 'Table'[Date] =_max),[Current Data] ) )