Calaculate the difference between one column if the other column contains a certain text

[MaighreadL]

Hi There. 

I was hoping you could help me with this. 

I have a table where I would like the difference to be calculated based on the item number 

So for example Item Number 22 I'd like the difference of landed unit cost between the current item number 22 and the previous one sold to return into another column 

I have created a calculated column with this formula

CalculatedDifference =
VAR PreviousItemNumber_ =
CALCULATE (
MAX ( Sheet1[Item Number] ),
Sheet1[Item Number] < EARLIER (Sheet1[Item Number]),
ALLEXCEPT ( Sheet1, Sheet1[Item Number] )
)
VAR PreviousLandedCost_ =
CALCULATE (
DISTINCT ( Sheet1[Landed Unit Cost] ),
Sheet1[Item Number] = PreviousItemNumber_,
ALLEXCEPT ( Sheet1, Sheet1[Item Number] )
)
VAR CurrentLandedCost_ = Sheet1[Landed Unit Cost]
RETURN
IF (
NOT ISBLANK ( CurrentLandedCost_ ) && NOT ISBLANK ( PreviousLandedCost_ ),
CurrentLandedCost_ - PreviousLandedCost_

But it is returning an error ;A table of multiple values was supplied where a single value was expected

Here is a copy of the table

DatePO NumberItem NumberLanded Unit Cost

Wednesday 1 January 2020	1	22	10
Thursday 2 January 2020	2	22	12
Friday 3 January 2020	3	11	2.86
Saturday 4 January 2020	4	11	2.85
Sunday 5 January 2020	5	11	2.84
Monday 6 January 2020	6	77	3.84
Tuesday 7 January 2020	7	77	3.89
Wednesday 8 January 2020	8	77	3.89
Thursday 9 January 2020	9	77	3.82
Friday 10 January 2020	10	77	3.75
Saturday 11 January 2020	11	77	3.75
Sunday 12 January 2020	12	77	3.75
Monday 13 January 2020	13	22	1.2
Tuesday 14 January 2020	14	22	1.2
Wednesday 15 January 2020	15	33	5
Thursday 16 January 2020	16	33	5.14
Friday 17 January 2020	17	33	5.12
Saturday 18 January 2020	18	33	5.12

Thank you ! 

[harshnathani · Accepted solution]

HI @MaighreadL ,

Create a Calculated Column

Difference =
VAR a =
    CALCULATE (
        MAX ( 'Table'[Date] ),
        FILTER (
            'Table',
            'Table'[Item Number]
                = EARLIER ( 'Table'[Item Number] )
                && 'Table'[Date]
                    < EARLIER ( 'Table'[Date] )
        )
    )
VAR b =
    CALCULATE (
        MAX ( 'Table'[Unit Cost] ),
        FILTER (
            'Table',
            'Table'[Item Number]
                = EARLIER ( 'Table'[Item Number] )
                && 'Table'[Date] = a
        )
    )
RETURN
    IF (
        b
            <> BLANK (),
        'Table'[Unit Cost] - b
    )

Regards,

Harsh Nathani

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[parry2k]

@MaighreadL I'm sure @harshnathani solution will work, I didn't look at it but it can have performance implications on a large dataset. I would add a measure using the following DAX expression:

Measure = 
VAR __tbl = ALL ( 'Table'[Id], 'Table'[DatePO] )
VAR __prevDate = CALCULATE ( MAX ( 'Table'[DatePO] ), FILTER ( __tbl, 'Table'[DatePO] < MAX ( 'Table'[DatePO] ) ) )
RETURN 
CALCULATE ( SUM ( 'Table'[Amount] ), __tbl, 'Table'[DatePO] = __prevDate)

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[MaighreadL]

@harshnathani  This is perfect !!! Thank you so much !!!