Flexible indexed values

[KoenStam]

(A) I have a relatively simple table with 2 column, one for the date and one containing daily market prices (of aluminium).

(B) I made a graph showing the daily prices over the time period covered by my data.

(C) Subsequently, I made a slicer for the date, making it possible to showing a more narrow time period. Besides, I made 2 measures, one showing the first date of the selected time period and one for the last date of my selected time period:

Firstdate = FIRSTDATE('Primary Aluminium'[Date])

Lastdate = LASTDATE('Primary Aluminium'[Date])

(D) I made 2 measures showing the related first and last price of the selected time period, using a visual level filter for the date.

Question> Now, what I want is to show on the graph is not the actual price per day, but the indexed price. Meaning that the starting price is 1 and the prices of the following days are shown relative to the price of the first day (e.g. instead of 2000 and 2200, it will show 1 and 1.1 for the first two days). The difficulty is that when I change the selected time period, the starting date (and therefore starting value changes), therefore the prices of the following days have to be divided by a different starting value. How to do this?

[v-chuncz-msft · Accepted solution]

@KoenStam,

You may add a measure as shown below.

Measure =
DIVIDE (
    SUM ( 'Primary Aluminium'[Close] ),
    CALCULATE (
        SUM ( 'Primary Aluminium'[Close] ),
        FIRSTDATE ( ALLSELECTED ( 'Primary Aluminium'[Date] ) )
    )
)

[KoenStam]

Many thanks, your reply solved my question!