"""Lifetime distributions."""
from __future__ import annotations
from abc import ABC
from collections.abc import Sequence
from typing import (
Any,
Literal,
Self,
final,
)
from typing_extensions import override
import numpy as np
import optype.numpy as onp
from numpydoc import docscrape # pyright: ignore[reportMissingTypeStubs]
from scipy.optimize import Bounds
from scipy.special import digamma, exp1, gamma, gammaincc, gammainccinv
from ._base import (
FittableParametricLifetimeModel,
LifetimeData,
LifetimeLikelihood,
ParametricLifetimeModel,
document_args,
)
from assetlife.base import FitConfig, FittingResults
from assetlife.quadratures import (
laguerre_quadrature,
)
from assetlife.typing import CoercibleFloat64_ND, Float64_ND
class LifetimeDistribution(FittableParametricLifetimeModel[()], ABC):
"""
Base class for distribution model.
"""
fitting_results: FittingResults | None
@override
@document_args(base_cls=ParametricLifetimeModel, args_docstring=[])
def sf(self, time: CoercibleFloat64_ND) -> Float64_ND:
return super().sf(time)
@override
@document_args(base_cls=ParametricLifetimeModel, args_docstring=[])
def isf(self, probability: CoercibleFloat64_ND) -> Float64_ND:
cumulative_hazard_rate = -np.log(
np.clip(probability, 0, 1 - np.finfo(float).resolution)
)
return self.ichf(cumulative_hazard_rate)
@override
@document_args(base_cls=ParametricLifetimeModel, args_docstring=[])
def cdf(self, time: CoercibleFloat64_ND) -> Float64_ND:
return super().cdf(time)
@override
@document_args(base_cls=ParametricLifetimeModel, args_docstring=[])
def pdf(self, time: CoercibleFloat64_ND) -> Float64_ND:
return super().pdf(time)
@override
@document_args(base_cls=ParametricLifetimeModel, args_docstring=[])
def ppf(self, probability: CoercibleFloat64_ND) -> Float64_ND:
return super().ppf(probability)
@override
@document_args(
base_cls=ParametricLifetimeModel,
args_docstring=[],
returns=[docscrape.Parameter("out", "np.float64", [""])],
)
def median(self) -> Float64_ND:
return self.ppf(0.5) # no super here to return np.float64
@override
@document_args(
base_cls=FittableParametricLifetimeModel,
args_docstring=[],
returns=[docscrape.Parameter("out", "np.float64", [""])],
)
def jac_sf(self, time: CoercibleFloat64_ND) -> onp.ArrayND[np.float64]:
return super().jac_sf(time)
@override
@document_args(
base_cls=FittableParametricLifetimeModel,
args_docstring=[],
returns=[docscrape.Parameter("out", "np.float64", [""])],
)
def jac_cdf(self, time: CoercibleFloat64_ND) -> onp.ArrayND[np.float64]:
return super().jac_cdf(time)
@override
@document_args(
base_cls=FittableParametricLifetimeModel,
args_docstring=[],
returns=[docscrape.Parameter("out", "np.float64", [""])],
)
def jac_pdf(self, time: CoercibleFloat64_ND) -> onp.ArrayND[np.float64]:
return super().jac_pdf(time)
@override
@document_args(base_cls=ParametricLifetimeModel, args_docstring=[])
def rvs(
self,
size: int | tuple[int, ...] | None = None,
*,
seed: int
| np.random.Generator
| np.random.BitGenerator
| np.random.RandomState
| None = None,
) -> Float64_ND:
return super().rvs(
size,
seed=seed,
)
@override
def init_likelihood(
self,
time: onp.Array1D[np.float64] | onp.Array[tuple[int, Literal[2]], np.float64],
args: Sequence[onp.Array1D[np.float64]] | None = None,
event: onp.Array1D[np.bool_] | None = None,
entry: onp.Array1D[np.float64] | None = None,
**kwargs: Any,
) -> LifetimeLikelihood:
assert args is None
lifetime_data = LifetimeData(time, event=event, entry=entry)
fresh_distrib = type(self)()
x0 = kwargs.get(
"x0", init_distrib_params_from_lifetimes(fresh_distrib, lifetime_data)
)
config = FitConfig(x0)
config.scipy_minimize_options["bounds"] = kwargs.get(
"bounds", get_distrib_params_bounds(fresh_distrib)
)
config.scipy_minimize_options["method"] = kwargs.get("method", "L-BFGS-B")
config.covariance_method = kwargs.get(
"covariance_method", "2point" if isinstance(fresh_distrib, Gamma) else "cs"
)
return LifetimeLikelihood(fresh_distrib, lifetime_data, config)
def fit(
self,
time: onp.Array1D[np.float64] | onp.Array[tuple[int, Literal[2]], np.float64],
event: onp.Array1D[np.bool_] | None = None,
entry: onp.Array1D[np.float64] | None = None,
**kwargs: Any,
) -> Self:
optimizer = self.init_likelihood(time, event=event, entry=entry, **kwargs)
self.fitting_results = optimizer.optimize()
self.set_params(self.fitting_results.optimal_params)
return self
def init_distrib_params_from_lifetimes(
model: LifetimeDistribution, data: LifetimeData
) -> onp.Array1D[np.float64]:
# flatten censored_time in case it is 2D
all_time_values = np.concatenate((
data.complete_time.flatten(),
data.censored_time.flatten(),
))
nb_params = model.get_params().size
if isinstance(model, Gompertz):
param0 = np.empty(nb_params, dtype=np.float64)
rate = np.pi / (np.sqrt(6) * np.std(all_time_values))
shape = np.exp(-rate * np.mean(all_time_values))
param0[0] = shape
param0[1] = rate
return param0
param0 = np.ones(nb_params, dtype=np.float64)
param0[-1] = 1 / np.median(all_time_values)
return param0
def get_distrib_params_bounds(model: LifetimeDistribution) -> Bounds:
nb_params = model.get_params().size
return Bounds(
np.full(nb_params, np.finfo(float).resolution),
np.full(nb_params, np.inf),
)
[docs]
@final
class Exponential(LifetimeDistribution):
r"""
Exponential lifetime distribution.
The exponential distribution is a 1-parameter distribution with
:math:`(\lambda)`. The probability density function is:
.. math::
f(t) = \lambda e^{-\lambda t}
where:
- :math:`\lambda > 0`, the rate parameter,
- :math:`t\geq 0`, the operating time, age, cycles, etc.
|
Parameters
----------
rate : float, default is None
Rate parameter.
Attributes
----------
fitting_results : FittingResults, default is None
An object containing fitting results (AIC, BIC, etc.).
If the model is not fitted, the value is None.
"""
def __init__(self, rate: float | None = None):
super().__init__(rate)
[docs]
@override
@document_args(base_cls=ParametricLifetimeModel, args_docstring=[])
def hf(self, time: CoercibleFloat64_ND) -> Float64_ND:
return self.get_params()[0] * np.ones_like(time)
[docs]
@override
@document_args(base_cls=ParametricLifetimeModel, args_docstring=[])
def chf(self, time: CoercibleFloat64_ND) -> Float64_ND:
return self.get_params()[0] * time
[docs]
@override
@document_args(base_cls=ParametricLifetimeModel, args_docstring=[])
def ichf(self, cumulative_hazard_rate: CoercibleFloat64_ND) -> Float64_ND:
return cumulative_hazard_rate / self.get_params()[0]
[docs]
@override
@document_args(
base_cls=FittableParametricLifetimeModel,
args_docstring=[],
returns=[docscrape.Parameter("out", "np.float64", [""])],
)
def jac_hf(self, time: CoercibleFloat64_ND) -> onp.ArrayND[np.float64]:
if isinstance(time, np.ndarray):
jac = np.expand_dims(np.ones_like(time, dtype=np.float64), axis=0)
else:
jac = np.array([1], dtype=np.float64)
return jac
[docs]
@override
@document_args(
base_cls=FittableParametricLifetimeModel,
args_docstring=[],
returns=[docscrape.Parameter("out", "np.float64", [""])],
)
def jac_chf(self, time: CoercibleFloat64_ND) -> onp.ArrayND[np.float64]:
if isinstance(time, np.ndarray):
jac = np.expand_dims(time, axis=0).astype(np.float64)
else:
jac = np.array([time], dtype=np.float64)
return jac
[docs]
@override
@document_args(
base_cls=FittableParametricLifetimeModel,
args_docstring=[],
returns=[docscrape.Parameter("out", "np.float64", [""])],
)
def dhf(self, time: CoercibleFloat64_ND) -> onp.ArrayND[np.float64]:
if isinstance(time, np.ndarray):
return np.zeros_like(time, dtype=np.float64)
return np.asarray(0, dtype=np.float64)
[docs]
@override
@document_args(
base_cls=FittableParametricLifetimeModel,
args_docstring=[],
returns=[docscrape.Parameter("out", "np.float64", [""])],
)
def mean(self) -> np.float64:
return 1 / self.get_params()[0]
[docs]
@override
@document_args(
base_cls=FittableParametricLifetimeModel,
args_docstring=[],
returns=[docscrape.Parameter("out", "np.float64", [""])],
)
def var(self) -> np.float64:
return 1 / self.get_params()[0] ** 2
[docs]
@override
@document_args(
base_cls=FittableParametricLifetimeModel,
args_docstring=[],
returns=[docscrape.Parameter("out", "np.float64", [""])],
)
def mrl(self, time: CoercibleFloat64_ND) -> Float64_ND:
"""
The mean residual life function.
Here, the exact mean residual life is computed.
Otherwise, `assetlife.lifetime_model.mrl` function.
Returns
-------
out : np.float64 or np.ndarray
"""
return 1 / self.get_params()[0] * np.ones_like(time)
@override
def __repr__(self) -> str:
return f"Exponential(rate={self.get_params()[0].item()!r})"
[docs]
@final
class Weibull(LifetimeDistribution):
r"""
Weibull lifetime distribution.
The Weibull distribution is a 2-parameter distribution with
:math:`(c,\lambda)`. The probability density function is:
.. math::
f(t) = c \lambda (\lambda t)^{c-1} e^{-(\lambda t)^c}
where:
- :math:`c > 0`, the shape parameter,
- :math:`\lambda > 0`, the rate parameter,
- :math:`t\geq 0`, the operating time, age, cycles, etc.
Parameters
----------
shape : float, default is None
Shape parameter.
rate : float, default is None
Rate parameter.
Attributes
----------
fitting_results : FittingResults, default is None
An object containing fitting results (AIC, BIC, etc.).
If the model is not fitted, the value is None.
nb_params
params
params_names
plot
shape
rate
"""
def __init__(self, shape: float | None = None, rate: float | None = None):
super().__init__(shape, rate)
[docs]
@override
@document_args(base_cls=LifetimeDistribution, args_docstring=[])
def hf(self, time: CoercibleFloat64_ND) -> Float64_ND:
shape, rate = self.get_params()
return shape * rate * (rate * np.asarray(time)) ** (shape - 1)
[docs]
@override
@document_args(base_cls=LifetimeDistribution, args_docstring=[])
def chf(self, time: CoercibleFloat64_ND) -> Float64_ND:
shape, rate = self.get_params()
return (rate * np.asarray(time)) ** shape
[docs]
@override
@document_args(base_cls=LifetimeDistribution, args_docstring=[])
def ichf(self, cumulative_hazard_rate: CoercibleFloat64_ND) -> Float64_ND:
shape, rate = self.get_params()
return np.asarray(cumulative_hazard_rate) ** (1 / shape) / rate
[docs]
@override
@document_args(
base_cls=FittableParametricLifetimeModel,
args_docstring=[],
returns=[docscrape.Parameter("out", "np.float64", [""])],
)
def jac_hf(self, time: CoercibleFloat64_ND) -> onp.ArrayND[np.float64]:
shape, rate = self.get_params()
return np.stack(
(
rate * (rate * time) ** (shape - 1) * (1 + shape * np.log(rate * time)),
shape**2 * (rate * time) ** (shape - 1),
),
)
[docs]
@override
@document_args(
base_cls=FittableParametricLifetimeModel,
args_docstring=[],
returns=[docscrape.Parameter("out", "np.float64", [""])],
)
def jac_chf(self, time: CoercibleFloat64_ND) -> onp.ArrayND[np.float64]:
shape, rate = self.get_params()
return np.stack(
(
np.log(rate * time) * (rate * time) ** shape,
shape * time * (rate * time) ** (shape - 1),
),
)
[docs]
@override
@document_args(
base_cls=FittableParametricLifetimeModel,
args_docstring=[],
returns=[docscrape.Parameter("out", "np.float64", [""])],
)
def dhf(self, time: CoercibleFloat64_ND) -> onp.ArrayND[np.float64]:
shape, rate = self.get_params()
return np.asarray(
shape * (shape - 1) * rate**2 * (rate * time) ** (shape - 2),
)
[docs]
@override
@document_args(
base_cls=FittableParametricLifetimeModel,
args_docstring=[],
returns=[docscrape.Parameter("out", "np.float64", [""])],
)
def mean(self) -> np.float64:
shape, rate = self.get_params()
return gamma(1 + 1 / shape) / rate
[docs]
@override
@document_args(
base_cls=FittableParametricLifetimeModel,
args_docstring=[],
returns=[docscrape.Parameter("out", "np.float64", [""])],
)
def var(self) -> np.float64:
shape, rate = self.get_params()
return gamma(1 + 2 / shape) / rate**2 - self.mean() ** 2
[docs]
@override
@document_args(
base_cls=FittableParametricLifetimeModel,
args_docstring=[],
returns=[docscrape.Parameter("out", "np.float64", [""])],
)
def mrl(self, time: CoercibleFloat64_ND) -> Float64_ND:
"""
The mean residual life function.
Here, the exact mean residual life is computed.
Otherwise, `assetlife.lifetime_model.mrl` function.
Returns
-------
out : np.float64 or np.ndarray
"""
shape, rate = self.get_params()
return (
gamma(1 / shape)
/ (rate * shape * self.sf(time))
* gammaincc(
1 / shape,
(rate * time) ** shape,
)
)
@override
def __repr__(self) -> str:
params = self.get_params()
return f"Weibull(shape={params[0].item()!r}, rate={params[1].item()!r})"
[docs]
@final
class Gompertz(LifetimeDistribution):
r"""
Gompertz lifetime distribution.
The Gompertz distribution is a 2-parameter distribution with
:math:`(c,\lambda)`. The probability density function is:
.. math::
f(t) = c \lambda e^{\lambda t} e^{ -c \left( e^{\lambda t}-1 \right) }
where:
- :math:`c > 0`, the shape parameter,
- :math:`\lambda > 0`, the rate parameter,
- :math:`t\geq 0`, the operating time, age, cycles, etc.
|
Parameters
----------
shape : float, default is None
Shape parameter.
rate : float, default is None
Rate parameter.
Attributes
----------
fitting_results : FittingResults, default is None
An object containing fitting results (AIC, BIC, etc.).
If the model is not fitted, the value is None.
"""
def __init__(self, shape: float | None = None, rate: float | None = None):
super().__init__(shape, rate)
[docs]
@override
@document_args(base_cls=LifetimeDistribution, args_docstring=[])
def hf(self, time: CoercibleFloat64_ND) -> Float64_ND:
shape, rate = self.get_params()
return shape * rate * np.exp(rate * time)
[docs]
@override
@document_args(base_cls=LifetimeDistribution, args_docstring=[])
def chf(self, time: CoercibleFloat64_ND) -> Float64_ND:
shape, rate = self.get_params()
return shape * np.expm1(rate * time)
[docs]
@override
@document_args(base_cls=LifetimeDistribution, args_docstring=[])
def ichf(self, cumulative_hazard_rate: CoercibleFloat64_ND) -> Float64_ND:
shape, rate = self.get_params()
return 1 / rate * np.log1p(cumulative_hazard_rate / shape)
[docs]
@override
@document_args(
base_cls=FittableParametricLifetimeModel,
args_docstring=[],
returns=[docscrape.Parameter("out", "np.float64", [""])],
)
def jac_hf(self, time: CoercibleFloat64_ND) -> onp.ArrayND[np.float64]:
shape, rate = self.get_params()
return np.stack(
(
rate * np.exp(rate * time),
shape * np.exp(rate * time) * (1 + rate * time),
),
)
[docs]
@override
@document_args(
base_cls=FittableParametricLifetimeModel,
args_docstring=[],
returns=[docscrape.Parameter("out", "np.float64", [""])],
)
def jac_chf(self, time: CoercibleFloat64_ND) -> onp.ArrayND[np.float64]:
shape, rate = self.get_params()
return np.stack(
(
np.expm1(rate * time),
shape * time * np.exp(rate * time),
),
)
[docs]
@override
@document_args(
base_cls=FittableParametricLifetimeModel,
args_docstring=[],
returns=[docscrape.Parameter("out", "np.float64", [""])],
)
def dhf(self, time: CoercibleFloat64_ND) -> onp.ArrayND[np.float64]:
shape, rate = self.get_params()
return shape * rate**2 * np.exp(rate * time)
[docs]
@override
@document_args(
base_cls=FittableParametricLifetimeModel,
args_docstring=[],
returns=[docscrape.Parameter("out", "np.float64", [""])],
)
def mean(self) -> np.float64:
shape, rate = self.get_params()
return np.exp(shape) * exp1(shape) / rate
[docs]
@override
@document_args(
base_cls=FittableParametricLifetimeModel,
args_docstring=[],
returns=[docscrape.Parameter("out", "np.float64", [""])],
)
def var(self) -> np.float64:
var = super().var()
assert isinstance(var, np.float64) # typeguard
return var
[docs]
@override
@document_args(
base_cls=FittableParametricLifetimeModel,
args_docstring=[],
returns=[docscrape.Parameter("out", "np.float64", [""])],
)
def mrl(self, time: CoercibleFloat64_ND) -> Float64_ND:
"""
The mean residual life function.
Here, the exact mean residual life is computed.
Otherwise, `assetlife.lifetime_model.mrl` function.
Returns
-------
out : np.float64 or np.ndarray
"""
shape, rate = self.get_params()
z = shape * np.exp(rate * time)
return np.exp(z) * exp1(z) / rate
@override
def __repr__(self) -> str:
params = self.get_params()
return f"Gompertz(shape={params[0].item()!r}, rate={params[1].item()!r})"
[docs]
@final
class Gamma(LifetimeDistribution):
r"""
Gamma lifetime distribution.
The Gamma distribution is a 2-parameter distribution with
:math:`(c,\lambda)`. The probability density function is:
.. math::
f(t) = \frac{\lambda^c t^{c-1} e^{-\lambda t}}{\Gamma(c)}
where:
- :math:`c > 0`, the shape parameter,
- :math:`\lambda > 0`, the rate parameter,
- :math:`t\geq 0`, the operating time, age, cycles, etc.
|
Parameters
----------
shape : float, default is None
Shape parameter.
rate : float, default is None
Rate parameter.
Attributes
----------
fitting_results : FittingResults, default is None
An object containing fitting results (AIC, BIC, etc.).
If the model is not fitted, the value is None.
"""
def __init__(self, shape: float | None = None, rate: float | None = None):
super().__init__(shape, rate)
def _uppergamma(self, x: CoercibleFloat64_ND) -> Float64_ND:
shape, _ = self.get_params()
x = np.asarray(x, dtype=np.float64)
return gammaincc(shape, x) * gamma(shape)
def _jac_uppergamma_shape(self, x: CoercibleFloat64_ND) -> Float64_ND:
shape, _ = self.get_params()
def func(
s: CoercibleFloat64_ND,
) -> Float64_ND:
return np.float64(np.log(s)) * s ** (shape - 1)
return laguerre_quadrature(func, x, deg=100)
[docs]
@override
@document_args(base_cls=LifetimeDistribution, args_docstring=[])
def hf(self, time: CoercibleFloat64_ND) -> Float64_ND:
shape, rate = self.get_params()
x = np.asarray(rate * time)
return rate * x ** (shape - 1) * np.exp(-x) / self._uppergamma(x)
[docs]
@override
@document_args(base_cls=LifetimeDistribution, args_docstring=[])
def chf(self, time: CoercibleFloat64_ND) -> Float64_ND:
shape, rate = self.get_params()
x = np.asarray(rate * time)
return np.log(gamma(shape)) - np.log(self._uppergamma(x))
[docs]
@override
@document_args(base_cls=LifetimeDistribution, args_docstring=[])
def ichf(self, cumulative_hazard_rate: CoercibleFloat64_ND) -> Float64_ND:
shape, rate = self.get_params()
return (
1
/ rate
* gammainccinv(
shape, np.exp(-np.asarray(cumulative_hazard_rate, dtype=np.float64))
)
)
[docs]
@override
@document_args(
base_cls=FittableParametricLifetimeModel,
args_docstring=[],
returns=[docscrape.Parameter("out", "np.float64", [""])],
)
def jac_hf(self, time: CoercibleFloat64_ND) -> onp.ArrayND[np.float64]:
shape, rate = self.get_params()
x = rate * time
y = x ** (shape - 1) * np.exp(-x) / self._uppergamma(x) ** 2
jac = (
y
* (
(rate * np.log(x) * self._uppergamma(x))
- rate * self._jac_uppergamma_shape(x)
),
y * ((shape - x) * self._uppergamma(x) + x**shape * np.exp(-x)),
)
return np.stack(jac)
[docs]
@override
@document_args(
base_cls=FittableParametricLifetimeModel,
args_docstring=[],
returns=[docscrape.Parameter("out", "np.float64", [""])],
)
def jac_chf(self, time: CoercibleFloat64_ND) -> onp.ArrayND[np.float64]:
shape, rate = self.get_params()
x = rate * time
jac = (
digamma(shape) - self._jac_uppergamma_shape(x) / self._uppergamma(x),
(x ** (shape - 1) * time * np.exp(-x) / self._uppergamma(x)),
)
return np.stack(jac)
[docs]
@override
@document_args(
base_cls=FittableParametricLifetimeModel,
args_docstring=[],
returns=[docscrape.Parameter("out", "np.float64", [""])],
)
def dhf(self, time: CoercibleFloat64_ND) -> onp.ArrayND[np.float64]:
shape, rate = self.get_params()
return np.asarray(
self.hf(time) * ((shape - 1) / time - rate + self.hf(time)),
)
[docs]
@override
@document_args(
base_cls=FittableParametricLifetimeModel,
args_docstring=[],
returns=[docscrape.Parameter("out", "np.float64", [""])],
)
def mean(self) -> np.float64:
shape, rate = self.get_params()
return shape / rate
[docs]
@override
@document_args(
base_cls=FittableParametricLifetimeModel,
args_docstring=[],
returns=[docscrape.Parameter("out", "np.float64", [""])],
)
def var(self) -> np.float64:
shape, rate = self.get_params()
return shape / (rate**2)
@override
def __repr__(self) -> str:
params = self.get_params()
return f"Gamma(shape={params[0].item()!r}, rate={params[1].item()!r})"
[docs]
@final
class LogLogistic(LifetimeDistribution):
r"""
Log-logistic probability distribution.
The Log-logistic distribution is defined as a 2-parameter distribution
:math:`(c, \lambda)`. The probability density function is:
.. math::
f(t) = \frac{c \lambda^c t^{c-1}}{(1+(\lambda t)^{c})^2}
where:
- :math:`c > 0`, the shape parameter,
- :math:`\lambda > 0`, the rate parameter,
- :math:`t\geq 0`, the operating time, age, cycles, etc.
|
Parameters
----------
shape : float, default is None
Shape parameter.
rate : float, default is None
Rate parameter.
Attributes
----------
fitting_results : FittingResults, default is None
An object containing fitting results (AIC, BIC, etc.).
If the model is not fitted, the value is None.
"""
def __init__(self, shape: float | None = None, rate: float | None = None):
super().__init__(shape, rate)
[docs]
@override
@document_args(base_cls=LifetimeDistribution, args_docstring=[])
def hf(self, time: CoercibleFloat64_ND) -> Float64_ND:
shape, rate = self.get_params()
x = rate * np.asarray(time)
return shape * rate * x ** (shape - 1) / (1 + x**shape)
[docs]
@override
@document_args(base_cls=LifetimeDistribution, args_docstring=[])
def chf(self, time: CoercibleFloat64_ND) -> Float64_ND:
shape, rate = self.get_params()
x = rate * time
return np.log(1 + x**shape)
[docs]
@override
@document_args(base_cls=LifetimeDistribution, args_docstring=[])
def ichf(self, cumulative_hazard_rate: CoercibleFloat64_ND) -> Float64_ND:
shape, rate = self.get_params()
return ((np.exp(cumulative_hazard_rate) - 1) ** (1 / shape)) / rate
[docs]
@override
@document_args(
base_cls=FittableParametricLifetimeModel,
args_docstring=[],
returns=[docscrape.Parameter("out", "np.float64", [""])],
)
def jac_hf(self, time: CoercibleFloat64_ND) -> onp.ArrayND[np.float64]:
shape, rate = self.get_params()
x = rate * time
jac = (
(rate * x ** (shape - 1) / (1 + x**shape) ** 2)
* (1 + x**shape + shape * np.log(rate * time)),
(rate * x ** (shape - 1) / (1 + x**shape) ** 2) * (shape**2 / rate),
)
return np.stack(jac)
[docs]
@override
@document_args(
base_cls=FittableParametricLifetimeModel,
args_docstring=[],
returns=[docscrape.Parameter("out", "np.float64", [""])],
)
def jac_chf(self, time: CoercibleFloat64_ND) -> onp.ArrayND[np.float64]:
shape, rate = self.get_params()
x = rate * time
jac = (
(x**shape / (1 + x**shape)) * np.log(rate * time),
(x**shape / (1 + x**shape)) * (shape / rate),
)
return np.stack(jac)
[docs]
@override
@document_args(
base_cls=FittableParametricLifetimeModel,
args_docstring=[],
returns=[docscrape.Parameter("out", "np.float64", [""])],
)
def dhf(self, time: CoercibleFloat64_ND) -> onp.ArrayND[np.float64]:
shape, rate = self.get_params()
x = rate * np.asarray(time)
return (
shape
* rate**2
* x ** (shape - 2)
* (shape - 1 - x**shape)
/ (1 + x**shape) ** 2
)
[docs]
@override
@document_args(
base_cls=FittableParametricLifetimeModel,
args_docstring=[],
returns=[docscrape.Parameter("out", "np.float64", [""])],
)
def mean(self) -> np.float64:
shape, rate = self.get_params()
b = np.pi / shape
if shape <= 1:
raise ValueError(f"Expectancy only defined for shape > 1: shape = {shape}")
return b / (rate * np.sin(b))
[docs]
@override
@document_args(
base_cls=FittableParametricLifetimeModel,
args_docstring=[],
returns=[docscrape.Parameter("out", "np.float64", [""])],
)
def var(self) -> np.float64:
shape, rate = self.get_params()
b = np.pi / shape
if shape <= 2:
raise ValueError(f"Variance only defined for shape > 2: shape = {shape}")
return (1 / rate**2) * (2 * b / np.sin(2 * b) - b**2 / (np.sin(b) ** 2))
@override
def __repr__(self) -> str:
params = self.get_params()
return f"LogLogistic(shape={params[0].item()!r}, rate={params[1].item()!r})"
