Measure to calculate current value minus previous row for a specific device

[Anonymous]

Hey!

I have the same problem for some time now that I really can't solve. I am doing a calculation to calculate the total energy,

I have following as example:

I have a column with an accumulative TotalEnergy for every device, I have the devices as dirfferent name, Index and I made a Rank with following formula (Where EndUtc is Date and time)

Rank = RANKX(FILTER(Data, Data[Device] = EARLIER(Data[Device])), Data[EndUtc],,ASC)

I wanna make a calculation NEWENERGYPERDAY: as for device A, 365-364 = 1, 364-364=0 etc, for every row. 

I have tried many different calculations, as for example: 

NewEnergyPer300s_kWh =

VAR minIndx = CALCULATE (

MAX ( Data[Index] ),

ALLEXCEPT ( Data, Data[Device] ),

Data[Index] < EARLIER (Data[Index] )

)

RETURN

IF (

ISBLANK ( minIndx ),

BLANK (),

Data[TotalEnergy_kWh]

    - CALCULATE (

               SUM ( Data[TotalEnergy_kWh] ),

                   Data[Index] = minIndx,

                       ALL ( Data )

)

)

which worked fine, except that I am getting not enough memory capacity, which is weird cause I don't even have too much data, and when I find other formulas and using function EARLIER I get the same issue evrytime, is it possible to write this formula or similar as a measure and not a column?

And also if there are any better way to write the calculation that will be better for the memory capcity?

Thanks! Feeling a bit lost with this issue. 

Kind regards

[Kristjan76 · Accepted solution]

Hi again,

Can you share your file? I am sorry but I think that I have overlooked some important facts in original post, but if you have created a Index column that increases with every new entry per device you should be able to use this calculated column. And perhaps you do not have to use the device varible at all (i.e. if i Index contains unique values)

EnergyPerDay =
VAR device = Data[Device]    // could be skipped
VAR ind = Data[Index]
VAR preInd= ind-1
VAR energyPreDate  = 
  SUMX(
    FILTER(
      Data,
      Data[Index] = preInd 
      && Data[Device] = device   // could also be skipped
    ),
    Data[TotalEnergy_kWh]
)

RETURN
Data[TotalEnergy_kWh] - energyPreDate

Best regars,

Kristjan