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ift
NIFTy
Commits
6b1c58f7
Commit
6b1c58f7
authored
Sep 13, 2018
by
Philipp Arras
Browse files
Add documentation to InverseGammaModel
parent
36c7db94
Changes
1
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Inline
Side-by-side
nifty5/library/inverse_gamma_model.py
View file @
6b1c58f7
...
...
@@ -31,6 +31,27 @@ from ..sugar import makeOp
class
InverseGammaModel
(
Operator
):
def
__init__
(
self
,
domain
,
alpha
,
q
):
"""Model which transforms a Gaussian into an inverse gamma distribution.
The pdf of the inverse gamma distribution is defined as follows:
.. math::
\f
rac {
\b
eta ^{
\a
lpha }}{\Gamma (
\a
lpha )}}x^{-
\a
lpha -1}\exp \left(-{
\f
rac {
\b
eta }{x}}
\r
ight)
That means that for large x the pdf falls off like x^(-alpha -1).
The mean of the pdf is at q / (alpha - 1) if alpha > 1.
The mode is q / (alpha + 1).
Parameters
----------
domain : Domain, tuple of Domain or DomainTuple
The domain on which the field shall be defined. This is at the same
time the domain and the target of the operator.
alpha : float
The alpha-parameter of the inverse-gamma distribution.
q : float
The q-parameter of the inverse-gamma distribution.
"""
self
.
_domain
=
self
.
_target
=
DomainTuple
.
make
(
domain
)
self
.
_alpha
=
alpha
self
.
_q
=
q
...
...
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