PLplot

Revision: 11608
          http://plplot.svn.sourceforge.net/plplot/?rev=11608&view=rev
Author:   hezekiahcarty
Date:     2011-03-07 00:51:46 +0000 (Mon, 07 Mar 2011)

Log Message:
-----------
Update OCaml example 27 to match the latest C example 27 changes

Modified Paths:
--------------
    trunk/examples/ocaml/x27.ml

Modified: trunk/examples/ocaml/x27.ml
===================================================================
--- trunk/examples/ocaml/x27.ml	2011-03-06 05:57:57 UTC (rev 11607)
+++ trunk/examples/ocaml/x27.ml	2011-03-07 00:51:46 UTC (rev 11608)
@@ -25,18 +25,35 @@
 
 open Plplot
 
+let pi = atan 1.0 *. 4.0
+
 let cycloid () = () (* TODO *)
 
+(* Calculate greatest common divisor following pseudo-code for the
+   Euclidian algorithm at http://en.wikipedia.org/wiki/Euclidean_algorithm *)
+let rec gcd a b =
+  let a = abs a in
+  let b = abs b in
+  match b with
+  | 0 -> a
+  | _ -> gcd b (a mod b)
+
 let spiro params fill =
-  let npnt = 20000 in
+  let npnt = 2000 in
   let xcoord = Array.make (npnt + 1) 0.0 in
   let ycoord = Array.make (npnt + 1) 0.0 in
 
   (* Fill the coordinates *)
 
-  let windings = int_of_float params.(3) in
+  (* Proper termination of the angle loop, very near the beginning
+     point, see
+     http://mathforum.org/mathimages/index.php/Hypotrochoid *)
+  let windings =
+    int_of_float (abs_float params.(1)) /
+      gcd (int_of_float params.(0)) (int_of_float params.(1))
+  in
   let steps = npnt / windings in
-  let dphi = 8.0 *. acos (-1.0) /. float_of_int steps in
+  let dphi = 2.0 *. pi /. float_of_int steps in
 
   (* This initialisation is safe! *)
   let xmin = ref 0.0 in
@@ -50,17 +67,24 @@
     xcoord.(i) <- (params.(0) -. params.(1)) *. cos phi +. params.(2) *. cos phiw;
     ycoord.(i) <- (params.(0) -. params.(1)) *. sin phi -. params.(2) *. sin phiw;
 
+    if i = 0 then (
+      xmin := xcoord.(i);
+      xmax := xcoord.(i);
+      ymin := ycoord.(i);
+      ymax := ycoord.(i);
+    )
+    else (
+    );
     if !xmin > xcoord.(i) then xmin := xcoord.(i) else ();
     if !xmax < xcoord.(i) then xmax := xcoord.(i) else ();
     if !ymin > ycoord.(i) then ymin := ycoord.(i) else ();
     if !ymax < ycoord.(i) then ymax := ycoord.(i) else ();
   done;
 
-  let scale = max (!xmax -. !xmin) (!ymax -. !ymin) in
-  let xmin = -0.65 *. scale in
-  let xmax = 0.65 *. scale in
-  let ymin = -0.65 *. scale in
-  let ymax = 0.65 *. scale in
+  let xmin = !xmin -. 0.15 *. (!xmax -. !xmin) in
+  let xmax = !xmax +. 0.15 *. (!xmax -. xmin) in
+  let ymin = !ymin -. 0.15 *. (!ymax -. !ymin) in
+  let ymax = !ymax +. 0.15 *. (!ymax -. ymin) in
 
   plwind xmin xmax ymin ymax;
 


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Revision: 11855
          http://plplot.svn.sourceforge.net/plplot/?rev=11855&view=rev
Author:   hezekiahcarty
Date:     2011-08-04 12:27:31 +0000 (Thu, 04 Aug 2011)

Log Message:
-----------
Update OCaml example 27 to add plarc section

Modified Paths:
--------------
    trunk/examples/ocaml/x27.ml

Modified: trunk/examples/ocaml/x27.ml
===================================================================
--- trunk/examples/ocaml/x27.ml	2011-08-04 11:53:47 UTC (rev 11854)
+++ trunk/examples/ocaml/x27.ml	2011-08-04 12:27:31 UTC (rev 11855)
@@ -101,6 +101,34 @@
     plline xcoord' ycoord';
   )
 
+let deg_to_rad x = x *. pi /. 180.0
+
+let arcs () =
+  let nseg = 8 in
+
+  let theta = ref 0.0 in
+  let dtheta = 360.0 /. float_of_int nseg in
+  plenv ~-.10.0 10.0 ~-.10.0 10.0 1 0;
+
+  (* Plot segments of circle in different colors *)
+  for i = 0 to nseg - 1 do
+    plcol0 (i mod 2 + 1);
+    plarc 0.0 0.0 8.0 8.0 !theta (!theta +. dtheta) 0.0 false;
+    theta := !theta +. dtheta;
+  done;
+
+  (* Draw several filled ellipses inside the circle at different
+     angles. *)
+  let a = 3.0 in
+  let b = a *. tan (deg_to_rad dtheta /. 2.0) in
+  theta := dtheta /. 2.0;
+  for i = 0 to nseg - 1 do
+    plcol0 (2 - i mod 2);
+    plarc (a *. cos (deg_to_rad !theta)) (a *. sin (deg_to_rad !theta)) a b 0.0 360.0 !theta true;
+    theta := !theta +. dtheta;
+  done;
+  ()
+
 (*--------------------------------------------------------------------------*\
  * Generates two kinds of plots:
  *   - construction of a cycloid (animated)
@@ -164,6 +192,9 @@
     spiro params.(i) true;
   done;
 
+  (* Finally, an example to test out plarc capabilities *)
+  arcs ();
+
   (* Don't forget to call plend() to finish off! *)
   plend ();
   ()


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