Commit afac0ec8 authored by Reimar H Leike's avatar Reimar H Leike
Browse files

changed Inverse Gamma likelihood to use the parameter convention from...

changed Inverse Gamma likelihood to use the parameter convention from wikipedia thus making it more general. Also added documentation
parent 3aaa3a70
......@@ -58,7 +58,7 @@ def make_adjust_variances(a,
"""
d = a*xi
d = (d.conjugate()*d).real
d = (d.conjugate()*d).real/2
n = len(samples)
if n > 0:
d_eval = 0.
......
......@@ -201,23 +201,41 @@ class PoissonianEnergy(EnergyOperator):
class InverseGammaLikelihood(EnergyOperator):
"""
FIXME
This describes the negative log-likelihood of the inverse gamma distribution.
It negative log-pdf(x) is given by
sum_i (alpha_i+1)*ln(x_i) + beta_i/x_i
This is the likelihood for the variance x=S_k given data beta = 0.5 |s_k|^2 where the Field s is known to have the covariance S_k.
Parameters
----------
beta : Field
beta parameter of the inverse gamma distribution
alpha : Scalar, Field, optional
alpha parameter of the inverse gamma distribution
"""
def __init__(self, d):
if not isinstance(d, Field):
def __init__(self, beta, alpha=-0.5):
if not isinstance(beta, Field):
raise TypeError
self._d = d
self._domain = DomainTuple.make(d.domain)
self._beta = beta
if np.isscalar(alpha):
alpha = Field.from_local_data(beta.domain, np.full(beta.local_data.shape, alpha+1))
elif not isinstance(alpha, Field):
raise TypeError
self._alphap1 = alpha+1
self._domain = DomainTuple.make(beta.domain)
def apply(self, x):
self._check_input(x)
res = 0.5*(x.log().sum() + (1./x).vdot(self._d))
res = x.log().vdot(self._alphap1) + (1./x).vdot(self._beta)
if not isinstance(x, Linearization):
return Field.scalar(res)
if not x.want_metric:
return res
metric = SandwichOperator.make(x.jac, makeOp(0.5/(x.val**2)))
metric = SandwichOperator.make(x.jac, makeOp(self._alphap1/(x.val**2)))
return res.add_metric(metric)
......
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