def model(M=10, N=100, D=3):
"""
Construct linear state-space model.
See, for instance, the following publication:
"Fast variational Bayesian linear state-space model"
Luttinen (ECML 2013)
"""
# Dynamics matrix with ARD
alpha = Gamma(1e-5, 1e-5, plates=(D, ), name='alpha')
A = GaussianARD(0,
alpha,
shape=(D, ),
plates=(D, ),
plotter=bpplt.GaussianHintonPlotter(rows=0,
cols=1,
scale=0),
name='A')
A.initialize_from_value(np.identity(D))
# Latent states with dynamics
X = GaussianMarkovChain(
np.zeros(D), # mean of x0
1e-3 * np.identity(D), # prec of x0
A, # dynamics
np.ones(D), # innovation
n=N, # time instances
plotter=bpplt.GaussianMarkovChainPlotter(scale=2),
name='X')
X.initialize_from_value(np.random.randn(N, D))
# Mixing matrix from latent space to observation space using ARD
gamma = Gamma(1e-5, 1e-5, plates=(D, ), name='gamma')
gamma.initialize_from_value(1e-2 * np.ones(D))
C = GaussianARD(0,
gamma,
shape=(D, ),
plates=(M, 1),
plotter=bpplt.GaussianHintonPlotter(rows=0,
cols=2,
scale=0),
name='C')
C.initialize_from_value(np.random.randn(M, 1, D))
# Observation noise
tau = Gamma(1e-5, 1e-5, name='tau')
tau.initialize_from_value(1e2)
# Underlying noiseless function
F = SumMultiply('i,i', C, X, name='F')
# Noisy observations
Y = GaussianARD(F, tau, name='Y')
Q = VB(Y, F, C, gamma, X, A, alpha, tau, C)
return Q
def model(M, N, D, K):
"""
Construct the linear state-space model with time-varying dynamics
For reference, see the following publication:
(TODO)
"""
#
# The model block for the latent mixing weight process
#
# Dynamics matrix with ARD
# beta : (K) x ()
beta = Gamma(1e-5, 1e-5, plates=(K, ), name='beta')
# B : (K) x (K)
B = GaussianARD(np.identity(K),
beta,
shape=(K, ),
plates=(K, ),
name='B',
plotter=bpplt.GaussianHintonPlotter(rows=0,
cols=1,
scale=0),
initialize=False)
B.initialize_from_value(np.identity(K))
# Mixing weight process, that is, the weights in the linear combination of
# state dynamics matrices
# S : () x (N,K)
S = GaussianMarkovChain(np.ones(K),
1e-6 * np.identity(K),
B,
np.ones(K),
n=N,
name='S',
plotter=bpplt.GaussianMarkovChainPlotter(scale=2),
initialize=False)
s = 10 * np.random.randn(N, K)
s[:, 0] = 10
S.initialize_from_value(s)
#
# The model block for the latent states
#
# Projection matrix of the dynamics matrix
# alpha : (K) x ()
alpha = Gamma(1e-5, 1e-5, plates=(D, K), name='alpha')
alpha.initialize_from_value(1 * np.ones((D, K)))
# A : (D) x (D,K)
A = GaussianARD(0,
alpha,
shape=(D, K),
plates=(D, ),
name='A',
plotter=bpplt.GaussianHintonPlotter(rows=0,
cols=1,
scale=0),
initialize=False)
# Initialize S and A such that A*S is almost an identity matrix
a = np.zeros((D, D, K))
a[np.arange(D), np.arange(D), np.zeros(D, dtype=int)] = 1
a[:, :, 0] = np.identity(D) / s[0, 0]
a[:, :, 1:] = 0.1 / s[0, 0] * np.random.randn(D, D, K - 1)
A.initialize_from_value(a)
# Latent states with dynamics
# X : () x (N,D)
X = VaryingGaussianMarkovChain(
np.zeros(D), # mean of x0
1e-3 * np.identity(D), # prec of x0
A, # dynamics matrices
S._convert(GaussianMoments)[1:], # temporal weights
np.ones(D), # innovation
n=N, # time instances
name='X',
plotter=bpplt.GaussianMarkovChainPlotter(scale=2),
initialize=False)
X.initialize_from_value(np.random.randn(N, D))
#
# The model block for observations
#
# Mixing matrix from latent space to observation space using ARD
# gamma : (D) x ()
gamma = Gamma(1e-5, 1e-5, plates=(D, ), name='gamma')
gamma.initialize_from_value(1e-2 * np.ones(D))
# C : (M,1) x (D)
C = GaussianARD(0,
gamma,
shape=(D, ),
plates=(M, 1),
name='C',
plotter=bpplt.GaussianHintonPlotter(rows=0,
cols=2,
scale=0))
C.initialize_from_value(np.random.randn(M, 1, D))
# Noiseless process
# F : (M,N) x ()
F = SumMultiply('d,d', C, X, name='F')
# Observation noise
# tau : () x ()
tau = Gamma(1e-5, 1e-5, name='tau')
tau.initialize_from_value(1e2)
# Observations
# Y: (M,N) x ()
Y = GaussianARD(F, tau, name='Y')
# Construct inference machine
Q = VB(Y, F, C, gamma, X, A, alpha, tau, S, B, beta)
return Q
import numpy as np
np.random.seed(1)
from bayespy.nodes import GaussianARD, GaussianMarkovChain, Gamma, Dot
M = 30
N = 400
D = 10
alpha = Gamma(1e-5, 1e-5, plates=(D, ), name='alpha')
A = GaussianARD(0, alpha, shape=(D, ), plates=(D, ), name='A')
X = GaussianMarkovChain(np.zeros(D),
1e-3 * np.identity(D),
A,
np.ones(D),
n=N,
name='X')
gamma = Gamma(1e-5, 1e-5, plates=(D, ), name='gamma')
C = GaussianARD(0, gamma, shape=(D, ), plates=(M, 1), name='C')
F = Dot(C, X, name='F')
C.initialize_from_random()
tau = Gamma(1e-5, 1e-5, name='tau')
Y = GaussianARD(F, tau, name='Y')
from bayespy.inference import VB
Q = VB(X, C, gamma, A, alpha, tau, Y)
w = 0.3
a = np.array([[np.cos(w), -np.sin(w), 0, 0], [np.sin(w),
np.cos(w), 0, 0], [0, 0, 1, 0],
[0, 0, 0, 0]])
c = np.random.randn(M, 4)
x = np.empty((N, 4))
f = np.empty((M, N))
y = np.empty((M, N))
x[0] = 10 * np.random.randn(4)
