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open Ast
(*
--# Normalize values
--#
--# Min-max normalize values to [0, 1].
--#
--# @name normalize
--# @param x :: Vector | List Numeric input.
--# @return :: Number | Vector Computed result (scalar or vectorized).
--# @family stats
--# @export
*)
let vecf xs = VVector (Array.of_list (List.map (fun x -> VFloat x) xs))
let register env =
Env.add "normalize" (make_builtin ~name:"normalize" 1 (fun args _ ->
let numeric_values 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 "normalize")
| _ -> Error (Error.type_error "Function `normalize` expects a numeric List or Vector.")
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 _ :: _ -> Error (Error.na_value_error "normalize")
| _ -> Error (Error.type_error "Function `normalize` requires numeric values.")
in
go [] vals
in
match args with
| [x] ->
(match numeric_values x with
| Error e -> e
| Ok [] -> VNA NAFloat
| Ok xs ->
let mn = List.fold_left min infinity xs in
let mx = List.fold_left max neg_infinity xs in
if mx = mn then Error.value_error "Function `normalize` undefined when min equals max."
else vecf (List.map (fun v -> (v -. mn) /. (mx -. mn)) xs))
| _ -> Error.arity_error_named "normalize" 1 (List.length args))) env