Hi Folks, Not sure if this will format correctly, but. Mathematica newbie here. Given :

data = <|"on" -> <|"A" -> <|Length -> 19, Total -> 8|>, 
    "B" -> <|Length -> 19, Total -> 8|>, 
    "C" -> <|Length -> 7, Total -> 0|>|>, 
  "off" -> <|"A" -> <|Length -> 9, Total -> 42|>, 
    "B" -> <|Length -> 7, Total -> 11|>, 
    "C" -> <|Length -> 9, Total -> 27|>|>|>;

(*Extract the columns (A,B,C,...)*)
columns = Keys[data["on"]];

(*Extract the data for "on" and "off"*)
extractRowData[status_] := 
  Map[Function[
    column, {data[status][column][Length], 
     data[status][column][Total]}], columns];

(*Construct the dataset with hierarchical columns*)
finalDataset = Dataset[
   Association[
    "on" ->
     AssociationThread[columns, extractRowData["on"]],
    "off" ->
     AssociationThread[columns, extractRowData["off"]]]][All,
  AssociationThread["group",
   Map[Function[column,
        Association["Length" -> #[[1]], 
         "Total" -> #[[2]]]], #1] & /@ # &]]

The finalDataset duplicates the Length, Total values row such that there are two row for on/off where there should be only one row for on/off. Looking at the finalDataset via //Normal show that the Length,Total element bit is being duplicated, but I cannot track where this happens though I suspect something in my "&/@#&" bit but its confusing me presently. Any help much appreciated. Thanks