Deedle Frame.Rows |> Series.windowWhile |> new frame with a new column computed from the windows?

Question

I am trying to use the Series.windowWhile function to window over rows of a Deedle frame. I want to calculate some statistics based on the window and then add the statistic back to the row.

The below code does not work once I get to the point of the last.Merge(length) line but it hopefully illustrates my goal:

type Person = 
  { Name:string; Age:int; Countries:string list; }

let peopleRecds = 
  [ { Name = "Joe"; Age = 51; Countries = [ "UK"; "US"; "UK"] }
    { Name = "Tomas"; Age = 28; Countries = [ "CZ"; "UK"; "US"; "CZ" ] }
    { Name = "Eve"; Age = 2; Countries = [ "FR" ] }
    { Name = "Suzanne"; Age = 15; Countries = [ "US" ] } ]
// Turn the list of records into data frame 
let peopleList = Frame.ofRecords peopleRecds
// Use the 'Name' column as a key (of type string)
let people = peopleList |> Frame.indexRowsInt "Age" |> Frame.sortRowsByKey
let newPeople =
    people.Rows
    |> Series.windowWhile (fun k1 k2 -> abs (k1 - k2) < 14)
    |> Series.mapValues (fun v ->
        let length = series ["length" => (v |> Series.values |> Seq.length)]
        let last = v |> Series.takeLast 1
        let newLast = last.Merge(length)
        newLast)
    |> Frame.ofRows

I want newPeople to be the people frame with a new column called length.

Answer 1

You problem is that v is an ObjectSeries<string> if all you need is to add the calculated length from your mapValues you can do it this way:

let newPeople' =
    people.Rows
    |> Series.windowWhile (fun k1 k2 -> abs (k1 - k2) < 14)
    |> Series.mapValues (fun v ->
        series ["length" => (v |> Series.values |> Seq.length)]    
    )
    |> Frame.ofRows

people.Merge(newPeople')