Source code for gluonts.distribution.poisson

# Copyright 2018 Amazon.com, Inc. or its affiliates. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License").
# You may not use this file except in compliance with the License.
# A copy of the License is located at
#
#     http://www.apache.org/licenses/LICENSE-2.0
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# or in the "license" file accompanying this file. This file is distributed
# on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
# express or implied. See the License for the specific language governing
# permissions and limitations under the License.

# Standard library imports
from typing import Dict, Optional, Tuple, List

# Third-party imports
import numpy as np

# First-party imports
from gluonts.model.common import Tensor
from gluonts.core.component import validated

# Relative imports
from .distribution import Distribution, _sample_multiple, getF, softplus
from .distribution_output import DistributionOutput


[docs]class Poisson(Distribution): r""" Poisson distribution, i.e. the distribution of the number of successes in a specified region. Parameters ---------- rate Tensor containing the means, of shape `(*batch_shape, *event_shape)`. F """ is_reparameterizable = False @validated() def __init__(self, rate: Tensor, F=None) -> None: self.rate = rate self.F = F if F else getF(rate) @property def batch_shape(self) -> Tuple: return self.rate.shape @property def event_shape(self) -> Tuple: return () @property def event_dim(self) -> int: return 0
[docs] def log_prob(self, x: Tensor) -> Tensor: F = self.F ll = x * F.log(self.rate) - F.gammaln(x + 1.0) - self.rate return ll
@property def mean(self) -> Tensor: return self.rate @property def stddev(self) -> Tensor: return self.F.sqrt(self.rate)
[docs] def sample( self, num_samples: Optional[int] = None, dtype=np.float32 ) -> Tensor: def s(rate: Tensor) -> Tensor: return self.F.random.poisson(lam=rate, dtype=dtype) return _sample_multiple(s, rate=self.rate, num_samples=num_samples)
@property def args(self) -> List: return [self.rate]
[docs]class PoissonOutput(DistributionOutput): args_dim: Dict[str, int] = {"rate": 1} distr_cls: type = Poisson
[docs] @classmethod def domain_map(cls, F, rate): rate = softplus(F, rate) + 1e-8 return rate.squeeze(axis=-1)
# Overwrites the parent class method. # We cannot scale using the affine transformation since Poisson should return integers. # Instead we scale the parameters.
[docs] def distribution( self, distr_args, loc: Optional[Tensor] = None, scale: Optional[Tensor] = None, ) -> Poisson: rate = distr_args if scale is None: return Poisson(rate) else: F = getF(rate) rate = F.broadcast_mul(rate, scale) return Poisson(rate, F)
@property def event_shape(self) -> Tuple: return ()