def submodel(self, states=None, obs=None, mincount_connectivity='1/n'):
"""Returns a HMM with restricted state space
Parameters
----------
states : None, str or int-array
Hidden states to restrict the model to. In addition to specifying
the subset, possible options are:
* None : all states - don't restrict
* 'populous-strong' : strongly connected subset with maximum counts
* 'populous-weak' : weakly connected subset with maximum counts
* 'largest-strong' : strongly connected subset with maximum size
* 'largest-weak' : weakly connected subset with maximum size
obs : None, str or int-array
Observed states to restrict the model to. In addition to specifying
an array with the state labels to be observed, possible options are:
* None : all states - don't restrict
* 'nonempty' : all states with at least one observation in the estimator
mincount_connectivity : float or '1/n'
minimum number of counts to consider a connection between two states.
Counts lower than that will count zero in the connectivity check and
may thus separate the resulting transition matrix. Default value:
1/nstates.
Returns
-------
hmm : HMM
The restricted HMM.
"""
if states is None and obs is None and mincount_connectivity == 0:
return self
if states is None:
states = _np.arange(self.nstates)
if obs is None:
obs = _np.arange(self.nstates_obs)
if str(mincount_connectivity) == '1/n':
mincount_connectivity = 1.0/float(self.nstates)
# handle new connectivity
from bhmm.estimators import _tmatrix_disconnected
S = _tmatrix_disconnected.connected_sets(self.count_matrix,
mincount_connectivity=mincount_connectivity,
strong=True)
if len(S) > 1:
# keep only non-negligible transitions
C = _np.zeros(self.count_matrix.shape)
large = _np.where(self.count_matrix >= mincount_connectivity)
C[large] = self.count_matrix[large]
for s in S: # keep all (also small) transition counts within strongly connected subsets
C[_np.ix_(s, s)] = self.count_matrix[_np.ix_(s, s)]
# re-estimate transition matrix with disc.
P = _tmatrix_disconnected.estimate_P(C, reversible=self.reversible, mincount_connectivity=0)
pi = _tmatrix_disconnected.stationary_distribution(P, C)
else:
C = self.count_matrix
P = self.transition_matrix
pi = self.stationary_distribution
# determine substates
if isinstance(states, str):
from bhmm.estimators import _tmatrix_disconnected
strong = 'strong' in states
largest = 'largest' in states
S = _tmatrix_disconnected.connected_sets(self.count_matrix, mincount_connectivity=mincount_connectivity,
strong=strong)
if largest:
score = [len(s) for s in S]
else:
score = [self.count_matrix[_np.ix_(s, s)].sum() for s in S]
states = _np.array(S[_np.argmax(score)])
if states is not None: # sub-transition matrix
self._active_set = states
C = C[_np.ix_(states, states)].copy()
P = P[_np.ix_(states, states)].copy()
P /= P.sum(axis=1)[:, None]
pi = _tmatrix_disconnected.stationary_distribution(P, C)
self.initial_count = self.initial_count[states]
self.initial_distribution = self.initial_distribution[states] / self.initial_distribution[states].sum()
# determine observed states
if str(obs) == 'nonempty':
import msmtools.estimation as msmest
obs = _np.where(msmest.count_states(self.discrete_trajectories_lagged) > 0)[0]
if obs is not None:
# set observable set
self._observable_set = obs
self._nstates_obs = obs.size
# full2active mapping
_full2obs = -1 * _np.ones(self._nstates_obs_full, dtype=int)
_full2obs[obs] = _np.arange(len(obs), dtype=int)
# observable trajectories
self._dtrajs_obs = []
for dtraj in self.discrete_trajectories_full:
self._dtrajs_obs.append(_full2obs[dtraj])
# observation matrix
B = self.observation_probabilities[_np.ix_(states, obs)].copy()
B /= B.sum(axis=1)[:, None]
else:
B = self.observation_probabilities
# set quantities back.
self.update_model_params(P=P, pobs=B, pi=pi)
self.count_matrix_EM = self.count_matrix[_np.ix_(states, states)] # unchanged count matrix
self.count_matrix = C # count matrix consistent with P
return self
def weakly_connected_sets(self):
return _tmatrix_disconnected.connected_sets(self._Tij, strong=False)
def weakly_connected_sets(self):
return _tmatrix_disconnected.connected_sets(self._Tij, strong=False)
def strongly_connected_sets(self):
return _tmatrix_disconnected.connected_sets(self._Tij, strong=True)
def strongly_connected_sets(self):
return _tmatrix_disconnected.connected_sets(self._Tij, strong=True)
