New column that calculates values ​​based on the last month of December

[nok]

Hello!
I have a table that follows this structure:

id	month	monthly price
111	01/12/2023	3528,58
111	01/01/2024	3659,41
111	01/02/2024	4866,62
111	01/03/2024	6650,90
222	01/12/2023	1000,10
222	01/01/2024	2000,20
222	01/02/2024	3000,30

I want to create a new column that does the following calculation, by each different id:
(((monthly price / last December's monthly price) -1) *100) + 100

The expected result would be something like this:

id	month	monthly price	new column
111	01/12/2023	3528,58	(value based on December 2022)
111	01/01/2024	3659,41	103,7077
111	01/02/2024	4866,62	137,9201
111	01/03/2024	6650,90	188,4866
222	01/12/2023	1000,10	(value based on December 2022)
222	01/01/2024	2000,20	200
222	01/02/2024	3000,30	300

How can I make this new column?

[Greg_Deckler · Accepted solution]

@nok See PBIX attached below signature.

Column = 
    VAR __Min = MIN( 'Table'[month] )
    VAR __id = [id]
    VAR __LastDecember = DATE( YEAR( [month] ) - 1, 12, 1 )
    VAR __LastDecValue = MAXX( FILTER( 'Table', [id] = __id && [month] = __LastDecember ), [monthly price] )
    VAR __Result = IF( [month] = __Min, BLANK(), ( ( ( [monthly price] / __LastDecValue ) - 1 ) * 100 ) + 100 )
RETURN
    __Result

[nok]

Amazing!!
Thanks for the great solution, @Greg_Deckler