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fc329a3 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 | """Pure-scale heterogeneity with heavy-tailed ILR noise."""
import numpy as np
from .base import DGPSample
from .pure_scale import PureScaleDGP
from ..utils.simplex import aitchison_dist, ilr, ilr_inv
class HeavyTailDGP(PureScaleDGP):
"""D2 with Student-t noise in ILR space."""
def __init__(
self,
K: int = 3,
sigma_min: float = 0.1,
c: float = 0.5,
d_x: int = 2,
df: float = 3.0,
):
super().__init__(K=K, sigma_min=sigma_min, c=c, d_x=d_x)
self.df = df
def sample(self, n: int, rng: np.random.Generator) -> DGPSample:
self._init_weights(rng)
X = rng.standard_normal((n, self.d_x))
mu = self._mu(X)
sigma = self._sigma(mu)
Z_mu = ilr(mu)
scale = np.sqrt(self.df / (self.df - 2.0)) if self.df > 2 else 1.0
eps = rng.standard_t(df=self.df, size=(n, self.K - 1)) / scale
Y = ilr_inv(Z_mu + sigma[:, None] * eps, K=self.K)
U = mu
R = aitchison_dist(Y, U)
return DGPSample(X=X, Y=Y, U=U, R=R, sigma_true=sigma)
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