How can I subtract 2 columns with to get the Difference from 1 Year

[Syndicate_Admin]

Hello I am Using Power Bi and using Python,

I have 2 columnes as "Date" and "profit"

like this and want to calculate the "Difference from 1 year Profit" column

The Dates are doubled but the same Profit value

I want to geht the difference but how can I do that?
The differenz from year 2019 should be 0 cause there is no year 2018

What I want ist always the = Profit from actual Year - (Profit from last year)
So the Month has to be the same only the year need to be changed in the Calculation

Date	Profit	Difference from 1 Year Profit
01.09.2019	100	0
01.09.2019	100	0
01.09.2019	100	0
01.09.2019	100	0
01.09.2019	100	0
01.09.2019	100	0
01.09.2019	100	0
01.10.2019	110	0
01.10.2019	110	0
01.10.2019	110	0
01.09.2020	320	220

Is there a Python script in which I can calculate these?

[Syndicate_Admin]

It is best pratice to create a Calendar dimenstion with a date column and  year offset column.
learn here .. Calendar Table training

Then create a one to many relationship by date to your fact table.
Then create measures to get this year and last years values.
Then use those values to get the difference.
See this example 

This solution works! So please be polite and give thanks and click the accept as solution and thumbs up button.

Year Difference = 
VAR thisyear = CALCULATE(SUM(Balance[Balance]),'Calendar'[Year offset] = 0)
VAR lastyear = CALCULATE(SUM(Balance[Balance]),'Calendar'[Year offset] =-1)
RETURN
 lastyear -  thisyear 

[Syndicate_Admin]

Hi @Cango 

You can create a blank query and put the following code to advanced editor in power query

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMjIwtNQ31LdU0lEyNDBQitUZQCFDA5CYIaliRgZQ44yNgEKxAA==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Date = _t, Profit = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Date", type date}, {"Profit", Int64.Type}}),
    #"Added Custom" = Table.AddColumn(#"Changed Type", "Last_year", each List.Min(Table.SelectRows(#"Changed Type",(x)=>x[Date]=Date.AddYears([Date],-1))[Profit])),
    #"Added Custom1" = Table.AddColumn(#"Added Custom", "Difference", each if [Last_year]<>null then [Profit]-[Last_year] else 0)
in
    #"Added Custom1"

Output

Best Regards!

Yolo Zhu

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