Stack & unstack about deedle HOT 1 CLOSED

/// Implements R-like 'stack' (returns frame whose 
/// columns are named Row/Column/Value)
let stack (frame:Frame<'R, 'C>) =
  frame.Rows.Observations |> Seq.collect (fun (KeyValue(rowKey, row)) ->
    row.Observations |> Seq.map (fun (KeyValue(colKey, value)) -> 
      Series.ofValues [box rowKey; box colKey; box value ]))
  |> Seq.mapi (fun i row -> i, row)
  |> Frame.ofRows
  |> Frame.indexColsWith ["Row"; "Column"; "Value"]

// Stack sample data frame (tested on small-ish frame with ~6k rows)
let stacked = frame |> stack 

// Unstack is easier, we just need to get three-element tuples from the frame and use Frame.ofValues
stacked.Rows.Values
|> Seq.map (fun row -> row.GetAs<DateTime>("Row"), row.GetAs<string>("Column"), row.Get("Value") )
|> Frame.ofValues