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Correction to vonmisesvariate() by Magnus Kessler: it should take and 

return something between 0 and 2*pi.  Also added a reference to the
literature.
This commit is contained in:
Guido van Rossum 1998-04-06 14:12:13 +00:00
parent 56c04b8376
commit 5810297052
1 changed files with 12 additions and 5 deletions
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17
Lib/random.py
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@ -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 --------------------