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Averages/Mean time of day: Difference between revisions
added ocaml
(Draft task that I will come back to tonight. (Sometime before that average :-)) |
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:<code>23:00:17, 23:40:20, 00:12:45, 00:17:19</code>
Using the idea that their are twenty four hours in a day which is analogous to their being 360 degrees in a circle, map times of day to and from angles and using the ideas of [[Averages/Mean angle]] compute and show here the average time of the nocturnal activity to an accuracy of a second of time.
=={{header|OCaml}}==
<lang ocaml>let pi_twice = 2.0 *. 3.14159_26535_89793_23846_2643
let day = float (24 * 60 * 60)
let rad_of_time t =
t *. pi_twice /. day
let time_of_rad r =
r *. day /. pi_twice
let mean_angle angles =
let sum_sin = List.fold_left (fun sum a -> sum +. sin a) 0.0 angles
and sum_cos = List.fold_left (fun sum a -> sum +. cos a) 0.0 angles in
let n = float (List.length angles) in
atan2 (sum_sin /. n) (sum_cos /. n)
let mean_time times =
let angles = List.map rad_of_time times in
let t = time_of_rad (mean_angle angles) in
if t < 0.0 then t +. day else t
let parse_time t =
Scanf.sscanf t "%d:%d:%d" (fun h m s -> float (s + m * 60 + h * 3600))
let round x = int_of_float (floor (x +. 0.5))
let string_of_time t =
let t = round t in
let h = t / 3600 in
let rem = t mod 3600 in
let m = rem / 60 in
let s = rem mod 60 in
Printf.sprintf "%d:%d:%d" h m s
let () =
let times = ["23:00:17"; "23:40:20"; "00:12:45"; "00:17:19"] in
Printf.printf "The mean time of [%s] is: %s\n"
(String.concat "; " times)
(string_of_time (mean_time (List.map parse_time times)))</lang>
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