Power BI relativity measure with mutiple groups - r

Question

I have a data that I simply create:
Col1 Col2 Col3 Col4
2014/1/1 A Y 10
2014/4/1 A Y 15
2015/1/1 A Z 15
2015/4/1 A Z 30
2014/1/1 B Y 20
2014/4/1 B Y 30
2015/1/1 B Z 40
2015/4/1 B Z 80
I want to create a measure in Power BI so I can create an interactive visualization. The above data is created for example so we need to suppose that col2, col3 have multiple factors.
The measure I want is relativity, the value in Col4 divide the first value under Col1 and Col2.
Result I supposed but I do not need this in data table since when I create the visualization and add the filter for other columns, Col5, Col6, and etc. that I did not show in this example:
Col1 Col2 Col3 Col4 relativity_Col3ALL relativity_Col3EqualsYorZ
2014/1/1 A Y 10 1 1
2014/4/1 A Y 15 1.5 1.5
2015/1/1 A Z 15 1.5 1
2015/4/1 A Z 30 3 2
2014/1/1 B Y 20 1 1
2014/4/1 B Y 30 1.5 1.5
2015/1/1 B Z 40 2 1
2015/4/1 B Z 80 4 2
So I plot it and add filters beside the plot. When I select Y in the filter Col3, the plot will automatically change.
I provide the code I think in R:
dt <- data.table::as.data.table(dt)
dt[, relativity := Col4 / Col4[1], by = .(Col1, Col2)]
But above code is incorrect because it did not consider Col3. I just want to mention Col4 / Col4[1] or Col4 / first(Col4).
I tried measure in Power BI:
relativity = CALCULATE(DIVIDE(dt[Col4], dt[AnotherMeasure]), MIN(dt[Col1]))
I know this is false.
Can anyone help?
UPDATE
I tried #Alexis Olson's code and modified as:
relativity =
VAR YR = MIN(dt[Col1].[Year])
VAR QT = MIN(dt[Col1].[Quarter])
VAR PF = CALCULATE(TOTALQTD(SUM(dt[Col4]), dt[Col1].[Date]), dt[Col1].[Year] = YR, dt[Col1].[Quarter] = QT)
RETURN
DIVIDE(SUM(dt[Col4]), PF)
However, when I visualize in the report, it all shows 1.
I also tried this:
relativity =
VAR YR = CALCULATE(MIN(dt[Col1].[Year]), ALLEXCEPT(dt, dt[Col2]))
VAR QT = CALCULATE(MIN(dt[Col1].[Quarter]), ALLEXCEPT(dt, dt[Col2]))
VAR PFQTD = TOTALQTD(SUM(dt[Col4]), dt[Col1].[Date])
VAR MPFQTD = CALCULATE(MAX(PFQTD), FILTER(dt, dt[Col1].[Year] = YR), FILTER(dt, dt[Col1].[Quarter] = QT))
RETURN
MPFQTD
Failed either

Answer 1

Using the logic from this Q&A, you can create a calculated column as follows:
relativity =
VAR FirstCol1 = CALCULATE ( MIN ( dt[Col1] ), ALLEXCEPT ( dt, dt[Col2], dt[Col3] ) )
VAR FirstCol4 = CALCULATE ( VALUES ( dt[Col4] ), dt[Col1] = FirstCol1 )
RETURN
DIVIDE ( dt[Col4], FirstCol4 )
This looks up the first date when Col2 and Col3 are the same value, then finds the Col4 value on that first date, and finally divides the current Col4 value by that first Col4 value.
The ALLEXCEPT removes the row context except for the columns you specify. If you want relativity_Col3_All, then simply remove that column from the ALLEXCEPT specification.