From 1b4d9ba83e708088c19719fe6d7c2bfa9fefc2c0 Mon Sep 17 00:00:00 2001
From: John Benediktsson <mrjbq7@gmail.com>
Date: Fri, 30 Mar 2012 19:43:51 -0700
Subject: [PATCH] random: adding von-mises distribution.
---
basis/random/random.factor | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)
diff --git a/basis/random/random.factor b/basis/random/random.factor
index ecfd037472..59a83e3305 100644
--- a/basis/random/random.factor
+++ b/basis/random/random.factor
@@ -190,6 +190,31 @@ ERROR: too-many-samples seq n ;
[ 1. gamma-random-float ] dip over zero?
[ 2drop 0 ] [ 1. gamma-random-float dupd + / ] if ;
+:: von-mises-random-float ( mu kappa -- n )
+ ! Based upon an algorithm published in: Fisher, N.I.,
+ ! "Statistical Analysis of Circular Data", Cambridge
+ ! University Press, 1993.
+ kappa 1e-6 <= [
+ 2pi random-unit *
+ ] [
+ 4. kappa sq * 1. + sqrt 1. + :> a
+ a 2. a * sqrt - 2. kappa * / :> b
+ b sq 1. + 2. b * / :> r
+
+ 0 :> c! 0 :> _f! ! initialize locals
+ [
+ random-unit {
+ [ 2. c - c * < ] [ 1. c - exp c * <= ]
+ } 1|| not
+ ] [
+ random-unit pi * cos :> z
+ r z * 1. + r z + / _f!
+ r _f - kappa * c!
+ ] do while
+
+ mu 2pi mod _f cos random-unit 0.5 > [ + ] [ - ] if
+ ] if ;
+
{
{ [ os windows? ] [ "random.windows" require ] }
{ [ os unix? ] [ "random.unix" require ] }