1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
open Ast
(*
--# Median
--#
--# Compute median of numeric values.
--#
--# @name median
--# @param x :: Vector | List Numeric input.
--# @param na_rm :: Bool = false Remove NA values first.
--# @param weights :: Vector[Float] | List[Float] = NA Optional non-negative observation weights.
--# @return :: Number | Vector Computed result (scalar or vectorized).
--# @family stats
--# @export
*)
let has_na_rm named_args =
List.exists (fun (name, v) -> name = Some "na_rm" && match v with VBool true -> true | _ -> false) named_args
let strip_na_rm named_args =
List.filter (fun (name, _) -> name <> Some "na_rm") named_args |> List.map snd
let numeric_values ~label ~na_rm v =
let vals =
match v with
| VVector arr -> Ok (Array.to_list arr)
| VList items -> Ok (List.map snd items)
| VNA _ -> Error (Error.na_value_error ~na_rm:true label)
| _ -> Error (Error.type_error (Printf.sprintf "Function `%s` expects a numeric List or Vector." label))
in
match vals with
| Error e -> Error e
| Ok vals ->
let rec go acc = function
| [] -> Ok (List.rev acc)
| VInt n :: tl -> go (float_of_int n :: acc) tl
| VFloat f :: tl -> go (f :: acc) tl
| VNA _ :: tl when na_rm -> go acc tl
| VNA _ :: _ -> Error (Error.na_value_error ~na_rm:true label)
| _ -> Error (Error.type_error (Printf.sprintf "Function `%s` requires numeric values." label))
in
go [] vals
let quantile xs p =
let arr = Array.of_list xs in
let n = Array.length arr in
if n = 0 then None
else (
Array.sort compare arr;
let h = p *. float_of_int (n - 1) in
let lo = int_of_float (Float.floor h) in
let hi = min (lo + 1) (n - 1) in
let frac = h -. float_of_int lo in
Some (arr.(lo) +. frac *. (arr.(hi) -. arr.(lo))))
let register env =
Env.add "median" (make_builtin_named ~name:"median" ~variadic:true 1 (fun named_args _ ->
match Math_common.get_bool_flag "na_rm" false named_args with
| Error e -> e
| Ok na_rm ->
let args = Math_common.positional_args_without ["na_rm"; "weights"] named_args in
let weight_arg = Math_common.optional_named_arg "weights" named_args in
match args with
| [x] ->
(match weight_arg with
| Some weight_v ->
(match Math_utils.extract_numeric_array_with_weights ~label:"median" ~na_rm x weight_v with
| Error e -> e
| Ok (xs, ws) ->
(match Math_utils.weighted_quantile_array xs ws 0.5 with
| Some v -> VFloat v
| None -> VNA NAFloat))
| None ->
(match numeric_values ~label:"median" ~na_rm x with
| Error e -> e
| Ok [] -> VNA NAFloat
| Ok xs ->
(match quantile xs 0.5 with
| Some v -> VFloat v
| None -> VNA NAFloat)))
| args -> Error.arity_error_named "median" 1 (List.length args))) env