deedle - Filtering Rows in F# -

i have code have following frame , filter rows follows:

let dfff=  [ "year" => series [ 1 => 1990.0; 2 => 1991.00; 3 => 1992.0;  4 => 1993.0]   "gold"  => series [ 1 => 10.0; 2 => 10.00; 3 => 15.0; 4 => 20.0]    "silver"  => series [ 1 => 20.0; 2 => 30.00; 3 => 45.0; 4 => 55.0] ]  |> frame  let dfff2 = dfff |> frame.filterrows (fun key row  -> row?year <= 1992.0 ) 

why have write key in

frame.filterrows (fun key row  -> row?year <= 1992.0) 

if function depends on row? role key play here? appreciate if explain me logic. thanks!

in deedle, frames have row keys , column keys. in case, have frame<int, string> meaning row keys integers (just numbers) , column keys strings (column names) - might have dates or other more interesting things row keys.

the filterrows function gives row key row data. key parameter row key - in case, (uninteresting) int index, might e.g. useful date in other scenarios.

f# lets write _ explicitly ignore value:

let dfff2 = dfff |> frame.filterrows (fun _ row  -> row?year <= 1992.0 ) 

in series module, have series.filter , series.filtervalues first 1 gives key & value , second 1 gives value. so, follow same pattern , add frame.filterrowvalues.

this quite easy, if want contribute, please send pull request change somewhere around here :-).