def _fifi2fid(x):
x = kept_within(0.0, x)
cdf = cerlang(nshape, phasemean, x)
pdf = derlang(nshape, phasemean, x)
fi = cdf - prob
if pdf <= 0.0:
if fi == 0.0: fi2fid = 1.0
else: fi2fid = MAXFLOAT
else:
fi2fid = fi/pdf
return fi, fi2fid
def rerlang(self, nshape, phasemean, xmax=float('inf'), pmax=1.0):
"""
Generator of Erlang-distributed random variates.
Represents the sum of nshape exponentially distributed random variables,
each having the same mean value = phasemean. For nshape = 1 it works as
a generator of exponentially distributed random numbers.
"""
assert xmax >= 0.0, "xmax must be a non-negative float in rerlang!"
self._checkpmax(pmax, 'rerlang')
pmx = pmax
if xmax < float('inf'):
pmx = min(pmax, cerlang(nshape, phasemean, xmax))
p = pmx * self.runif01()
x = ierlang(p, nshape, phasemean)
return x
