DAX Formula Help

Hi    anthonjhnon1 
The issue is that the variable is missing the REMOVEFILTERS function, which is necessary to exclude the current selection.
Specifically, for VAR NonME_CIs = SUM('Sample IP'[nonME_CI]), we need to add REMOVEFILTERS on the slicer/filter selection to ensure we calculate the correct value.

CIs Test Fixed = 
VAR CIs = CALCULATE(
    SUM('Sample IP'[TotalCustomersAffected]),
    REMOVEFILTERS('Sample IP'[MajorEvent])
)
VAR NonME_CIs = CALCULATE(
    SUM('Sample IP'[nonME_CI]),
    REMOVEFILTERS('Sample IP'[MajorEvent])
)
VAR MajorEvent = SELECTEDVALUE('Sample IP'[MajorEvent])
VAR MEYes = CIs - NonME_CIs
VAR MENo  = NonME_CIs
RETURN
SWITCH(
    MajorEvent,
    "Y", MEYes,   
    "N", MENo,    
    CIs           
)

Sample data :  

Major event N:

Major event Y:

No selection :

Thanks 

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Hi anthonjhnon1  Did you try the remove filters at table level ? if your date is coming from aother table you need to add too to the variables 

CIs Test Fixed Table = 
VAR CIs = CALCULATE(
    SUM('Sample IP'[TotalCustomersAffected]),
    REMOVEFILTERS('Sample IP')
)
VAR NonME_CIs = CALCULATE(
    SUM('Sample IP'[nonME_CI]),
    REMOVEFILTERS('Sample IP')
)
VAR MajorEvent = SELECTEDVALUE('Sample IP'[MajorEvent])
VAR MEYes = CIs - NonME_CIs
VAR MENo  = NonME_CIs
RETURN
SWITCH(
    MajorEvent,
    "Y", MEYes,   
    "N", MENo,    
    CIs           
)

If the issue still exists please share your data model with sample data

Thanks 
If you found this helpful, please consider giving it a kudo and marking it as the accepted solution — it goes a long way in helping others facing the same issue.

For more Power BI tips and discussions, let’s connect on LinkedIn:
https://www.linkedin.com/in/natarajan-manivasagan

Cheers!

Could you try the measure below:

CIs Test =
VAR _MajorEvent =
    SELECTEDVALUE ( v_HistoricalOutageData_c[MajorEvent] )

VAR _TotalCI =
    CALCULATE (
        SUM ( v_HistoricalOutageData_c[TotalCustomersAffected] ),
        REMOVEFILTERS ( v_HistoricalOutageData_c[MajorEvent] )
    )

VAR _TotalNonME =
    CALCULATE (
        SUM ( v_HistoricalOutageData_c[nonME_CI] ),
        REMOVEFILTERS ( v_HistoricalOutageData_c[MajorEvent] )
    )

RETURN
    SWITCH (
        _MajorEvent,
        "N", _TotalNonME,
        "Y", _TotalCI - _TotalNonME,
        _TotalCI
    )

The issue is that variables in DAX aren't really variable, they're constants. They are only ever evaluated once, so trying to evaluate them again with a modified filter context will not work, they will still have their original value. If you need to change the filter context then you need to include the full definition of the variable again inside the calculate.

Natarajan_M I marked this as a solution because it does work and works exactly as I want it to. However its not the ultimate solution for me. I need to share this DAX measure with tons of other reports and this solution will require all those reports to include a ME table and Calendar table (which I most reports have). Can you help me understand why adding those two tables work?