Finding the Delta between 2 nested tables

[Astrua]

Hi All,

I have a list of data with 2 nested tables with before and after process data. How do I write the code to find the delta between the before and after table? row 1 and column 1 of [after] table subtract row 1 and column 1 of [before] table respectively for the rest of the data.

ID	before	after
1	Table	Table
2	Table	Table
3	Table	Table
4	Table	Table

The data in the nested table is like this

Before:

0.0522	0.0476	0.0439	0.0424
0.0356	0.0316	0.0286	0.0264
0.0221	0.0191	0.0162	0.0136
0.01	0.0079	0.0054	0.0033
-0.0008	-0.0011	-0.003	-0.0051

After:

-0.098	-0.0696	-0.0004	0.0482
-0.071	-0.0065	0.032	0.0284
-0.0023	0.0323	0.02	0.0004
0.036	0.023	-0.0012	-0.0203
0.0258	0.0013	-0.0191	-0.037

[lbendlin · Accepted solution]

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMlSK1YlWMgKTxmDSRCk2FgA=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [ID = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"ID", Int64.Type}}),
    #"Added Custom" = Table.AddColumn(#"Changed Type", "before", each Before),
    #"Added Custom1" = Table.AddColumn(#"Added Custom", "after", each After),
    #"Added Custom2" = Table.AddColumn(#"Added Custom1", "Column1", each [after]{[ID]-1}[Column1]-[before]{[ID]-1}[Column1]),
    #"Added Custom3" = Table.AddColumn(#"Added Custom2", "Column2", each [after]{[ID]-1}[Column2]-[before]{[ID]-1}[Column2]),
    #"Added Custom4" = Table.AddColumn(#"Added Custom3", "Column3", each [after]{[ID]-1}[Column3]-[before]{[ID]-1}[Column3]),
    #"Added Custom5" = Table.AddColumn(#"Added Custom4", "Column4", each [after]{[ID]-1}[Column4]-[before]{[ID]-1}[Column4])
in
    #"Added Custom5"