diff options
| -rw-r--r-- | Lib/random.py | 17 |
1 files changed, 12 insertions, 5 deletions
diff --git a/Lib/random.py b/Lib/random.py index 49921cb..221bef6 100644 --- a/Lib/random.py +++ b/Lib/random.py @@ -79,10 +79,17 @@ TWOPI = 2.0*pi verify('TWOPI', 6.28318530718) def vonmisesvariate(mu, kappa): - # mu: mean angle (in radians between 0 and 180 degrees) + # mu: mean angle (in radians between 0 and 2*pi) # kappa: concentration parameter kappa (>= 0) - # if kappa = 0 generate uniform random angle + + # Based upon an algorithm published in: Fisher, N.I., + # "Statistical Analysis of Circular Data", Cambridge + # University Press, 1993. + + # Thanks to Magnus Kessler for a correction to the + # implementation of step 4. + if kappa <= 1e-6: return TWOPI * random() @@ -104,11 +111,11 @@ def vonmisesvariate(mu, kappa): u3 = random() if u3 > 0.5: - theta = mu + 0.5*acos(f) + theta = (mu % TWOPI) + acos(f) else: - theta = mu - 0.5*acos(f) + theta = (mu % TWOPI) - acos(f) - return theta % pi + return theta # -------------------- gamma distribution -------------------- |