Power pivot DAX formula to count unique items in one column for every row in another column

[Aleksandar89]

I am trying to solve problem. I have in my dataset among others also columns named customer and product.
Customer can have many products and entries are repeated. I need to have a new column to give number of unique products based on every row of customer column.
Dataset is huge and it's needed to be done in power pivot.

Customer	Product	Distinct # of prod. For cust.
x	aaa
y	aaa
x	aaa
x	bbb
y	xxx
z	xxx
z	yyy
z	qqq

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[horseyride]

Choose customer column
Group .. choose advanced
Group by Customer
Count = Count Distinct Rows
add aggregation
Rows = All Rows
Expand resulting column and add Product Back

let
    Source = Excel.CurrentWorkbook(){[Name="Table1"]}[Content],
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Customer", type text}, {"Product", type text}}),
    #"Grouped Rows" = Table.Group(#"Changed Type", {"Customer"}, {{"Count", each Table.RowCount(Table.Distinct(_)), type number}, {"Rows", each _, type table}}),
    #"Expanded Rows" = Table.ExpandTableColumn(#"Grouped Rows", "Rows", {"Product"}, {"Product"})
in
    #"Expanded Rows"