Dynamic WoW Variance against a Persistent Historical Snapshot in Power BI

Hi Amirolia ,

Incremental refresh partitions are immutable once written. Week 12 data won't be touched when Week 13 refreshes : as long as RangeStart/RangeEnd correctly filter your SnapshotDate column.

Check whether the below approach works for you :
Instead of lookup and previous week I think you can use the calculate approach 

_LatestSnap = MAXX(ALL(Fact[SnapshotDate]), Fact[SnapshotDate])
_PrevSnap = MAXX(FILTER(ALL(Fact[SnapshotDate]), Fact[SnapshotDate] < [_LatestSnap]), Fact[SnapshotDate])

WoW Delta V1 =
CALCULATE(SUM(Fact[V1]), ALL(Fact[SnapshotDate]), Fact[SnapshotDate] = [_LatestSnap])
- CALCULATE(SUM(Fact[V1]), ALL(Fact[SnapshotDate]), Fact[SnapshotDate] = [_PrevSnap])


Use Analyze in Excel : it creates an ODC-connected PivotTable that stays live against your published semantic model. Users just hit Refresh in Excel.
Avoid Export > CSV that's static.

Thanks ,
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