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(* $Id: ex4.ml,v 1.2 2004-11-22 19:54:26 chris_77 Exp $ *)
(* Illustrate a simple animation displaying the Taylor expansion of sin *)
module P = Gnuplot
open Parse_args
let usleep t = ignore(Unix.select [] [] [] t)
let tsin d =
(* Compute the Taylor expansion of sin of order 2d+1 *)
let d = max d 0 in
let fac = ref 1.
and s = ref 1. in
let p = Array.init (d+1)
(fun i ->
let c = !s /. !fac in
let i2 = 2. *. float(i+1) in
let () =
fac := !fac *. i2 *. (i2 +. 1.);
s := -. !s in
c) in
fun x ->
(* Horner eval of the poly *)
let x2 = x *. x
and y = ref 0. in
for i = d downto 0 do
y := p.(i) +. !y *. x2
done;
!y *. x
let () =
let device = device 1 in
let g = P.init ?offline:(offline 1) device in
let b = 9. in
let f = Array.init 10 tsin in
P.env g ~xgrid:true 0. b (-2.) 2.;
P.pen g 2;
P.pen_width g 3.;
P.fx g sin 0. b;
P.pen g 1;
P.pen_width g 1.;
for i = 0 to Array.length f - 1 do
P.fx g f.(i) 0. b;
usleep 0.5;
done;
if device = P.X then usleep 2.;
P.close g
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