Add column with sepecific cell value

[DatNguyen]

I want create new column A16_2 base on value of first row A16 which use flexible way:

Index	A16	A16_2
0	3500	3500
1	null	3500
2	null	3500

I use Custom function from Edit Query in Excel.

I try some way like that:

1. if [A16] = null then [A16]{0} else [A16]
2. List.Average([A16])

But It NOT WORK. Could someone guide me how to create new column base on specificed value of 1 column?

[Vera_33 · Accepted solution]

Hi @DatNguyen 

When you call [A16], it is not a list, so what is your logic?

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMlDSUTI2NTBQitWJVjIEcvJKc3LAHCM4JxYA", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Index = _t, A16 = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Index", Int64.Type}, {"A16", Int64.Type}}),
    #"Added Custom" = Table.AddColumn(#"Changed Type", "yourNewColumn", each if [A16]=null then #"Changed Type"[A16]{0} else [A16]),
    #"Added Custom1" = Table.AddColumn(#"Added Custom", "Custom", each List.Average(#"Added Custom"[A16]))
in
    #"Added Custom1"