pyemma.msm.timescales_msm¶
-
pyemma.msm.
timescales_msm
(dtrajs, lags=None, nits=None, reversible=True, connected=True, weights='empirical', errors=None, nsamples=50, n_jobs=None, show_progress=True, mincount_connectivity='1/n', only_timescales=False, core_set=None, milestoning_method='last_core')¶ Implied timescales from Markov state models estimated at a series of lag times.
- Parameters
dtrajs (array-like or list of array-likes) – discrete trajectories
lags (int, array-like with integers or None, optional) – integer lag times at which the implied timescales will be calculated. If set to None (default) as list of lag times will be automatically generated. For a single int, generate a set of lag times starting from 1 to lags, using a multiplier of 1.5 between successive lags.
nits (int, optional) – number of implied timescales to be computed. Will compute less if the number of states are smaller. If None, the number of timescales will be automatically determined.
reversible (boolean, optional) – Estimate transition matrix reversibly (True) or nonreversibly (False)
connected (boolean, optional) – If true compute the connected set before transition matrix estimation at each lag separately
weights (str, optional) –
can be used to re-weight non-equilibrium data to equilibrium. Must be one of the following:
’empirical’: Each trajectory frame counts as one. (default)
’oom’: Each transition is re-weighted using OOM theory, see 5.
errors (None | 'bayes', optional) –
Specifies whether to compute statistical uncertainties (by default not), an which algorithm to use if yes. Currently the only option is:
’bayes’ for Bayesian sampling of the posterior
Attention: * The Bayes mode will use an estimate for the effective count matrix
that may produce somewhat different estimates than the ‘sliding window’ estimate used with
errors=None
by default.Computing errors can be// slow if the MSM has many states.
There are still unsolved theoretical problems in the computation of effective count matrices, and therefore the uncertainty interval and the maximum likelihood estimator can be inconsistent. Use this as a rough guess for statistical uncertainties.
nsamples (int, optional) – The number of approximately independent transition matrix samples generated for each lag time for uncertainty quantification. Only used if errors is not None.
n_jobs (int, optional) – how many subprocesses to start to estimate the models for each lag time.
show_progress (bool, default=True) – whether to show progress of estimation.
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. The default evaluates to 1/nstates.
only_timescales (bool, default=False) – If you are only interested in the timescales and its samples, you can consider turning this on in order to save memory. This can be useful to avoid blowing up memory with BayesianMSM and lots of samples.
core_set (None (default) or array like, dtype=int) – Definition of core set for milestoning MSMs. If set to None, replaces state -1 (if found in discrete trajectories) and performs milestone counting. No effect for Voronoi-discretized trajectories (default). If a list or np.ndarray is supplied, discrete trajectories will be assigned accordingly.
milestoning_method (str) – Method to use for counting transitions in trajectories with unassigned frames. Currently available: | ‘last_core’, assigns unassigned frames to last visited core
- Returns
itsobj
- Return type
ImpliedTimescales
object
Example
>>> from pyemma import msm >>> dtraj = [0,1,1,2,2,2,1,2,2,2,1,0,0,1,1,1,2,2,1,1,2,1,1,0,0,0,1,1,2,2,1] # mini-trajectory >>> ts = msm.its(dtraj, [1,2,3,4,5], show_progress=False) >>> print(ts.timescales) [[ 1.5... 0.2...] [ 3.1... 1.0...] [ 2.03... 1.02...] [ 4.63... 3.42...] [ 5.13... 2.59...]]
See also
ImpliedTimescales
The object returned by this function.
pyemma.plots.plot_implied_timescales
Implied timescales plotting function. Just call it with the
ImpliedTimescales
object produced by this function as an argument.
-
class
pyemma.msm.estimators.implied_timescales.
ImpliedTimescales
(*args, **kwargs)¶ Methods
estimate
(X, **params)- param X
discrete trajectories
fit
(X[, y])Estimates parameters - for compatibility with sklearn.
get_params
([deep])Get parameters for this estimator.
get_sample_conf
([conf, process])Returns the confidence interval that contains alpha % of the sample data
get_sample_mean
([process])Returns the sample means of implied timescales.
get_sample_std
([process])Returns the standard error of implied timescales.
get_timescales
([process])Returns the implied timescale estimates
load
(file_name[, model_name])Loads a previously saved PyEMMA object from disk.
save
(file_name[, model_name, overwrite, …])saves the current state of this object to given file and name.
set_params
(**params)Set the parameters of this estimator.
Attributes
-
estimate
(X, **params)¶ - Parameters
X (lists of integer arrays) – discrete trajectories
estimator (Estimator) – Estimator to be used for estimating timescales at each lag time.
lags (array-like with integers or None, optional) – integer lag times at which the implied timescales will be calculated. If set to None (default) as list of lagtimes will be automatically generated.
nits (int, optional) – maximum number of implied timescales to be computed and stored. If less timescales are available, nits will be set to a smaller value during estimation. None means the number of timescales will be automatically determined.
n_jobs (int, optional) – how many subprocesses to start to estimate the models for each lag time.
-
property
estimators
¶ Returns the estimators for all lagtimes.
-
property
fraction_of_frames
¶ Returns the fraction of frames used to compute the count matrix at each lag time. .. rubric:: Notes
In a list of discrete trajectories with varying lengths, the estimation at longer lag times will mean discarding some trajectories for which not even one count can be computed. This function returns the fraction of frames that was actually used in computing the count matrix.
Be aware: this fraction refers to the full count matrix, and not that of the largest connected set. Hence, the output is not necessarily the active fraction. For that, use the
activte_count_fraction
function of thepyemma.msm.MaximumLikelihoodMSM
class object or for HMM respectively.
-
get_sample_conf
(conf=0.95, process=None)¶ Returns the confidence interval that contains alpha % of the sample data
etc.
- Parameters
conf (float, default = 0.95) –
the confidence interval. Use:
conf = 0.6827 for 1-sigma confidence interval
conf = 0.9545 for 2-sigma confidence interval
conf = 0.9973 for 3-sigma confidence interval
- Returns
(L,R) – lower and upper timescales bounding the confidence interval
if process is None, will return two (l x k) arrays, where l is the number of lag times and k is the number of computed timescales.
if process is an integer, will return two (l)-arrays with the selected process time scale for every lag time
- Return type
(float[],float[]) or (float[][],float[][])
-
get_sample_mean
(process=None)¶ Returns the sample means of implied timescales. Only available if underlying estimator produces samples.
- Parameters
process (int or None, default = None) – index in [0:n-1] referring to the process whose timescale will be returned. By default, process = None and all computed process timescales will be returned.
- Returns
if process is None, will return a (l x k) array, where l is the number of lag times
and k is the number of computed timescales.
if process is an integer, will return a (l) array with the selected process time scale
for every lag time
-
get_sample_std
(process=None)¶ Returns the standard error of implied timescales. Only available if underlying estimator produces samples.
- Parameters
process (int or None, default = None) – index in [0:n-1] referring to the process whose timescale will be returned. By default, process = None and all computed process timescales will be returned.
- Returns
if process is None, will return a (l x k) array, where l is the number of lag times
and k is the number of computed timescales.
if process is an integer, will return a (l) array with the selected process time scale
for every lag time
-
get_timescales
(process=None)¶ Returns the implied timescale estimates
- Parameters
process (int or None, default = None) – index in [0:n-1] referring to the process whose timescale will be returned. By default, process = None and all computed process timescales will be returned.
- Returns
if process is None, will return a (l x k) array, where l is the number of lag times
and k is the number of computed timescales.
if process is an integer, will return a (l) array with the selected process time scale
for every lag time
-
property
lags
¶ Return the list of lag times for which timescales were computed.
-
property
lagtimes
¶ Return the list of lag times for which timescales were computed.
-
property
models
¶ Returns the models for all lagtimes.
-
property
nits
¶ Return the number of timescales.
-
property
number_of_timescales
¶ Return the number of timescales.
-
property
sample_mean
¶ Returns the sample means of implied timescales. Need to generate the samples first, e.g. by calling bootstrap
- Returns
timescales – mean timescales for all processes and lag times. l is the number of lag times and k is the number of computed timescales.
- Return type
ndarray((l x k), dtype=float)
-
property
sample_std
¶ Returns the standard error of implied timescales. Only available if underlying estimator produces samples.
- Returns
timescales – standard deviations of timescales for all processes and lag times. l is the number of lag times and k is the number of computed timescales.
- Return type
ndarray((l x k), dtype=float)
-
property
samples_available
¶ Returns True if samples are available and thus sample means, standard errors and confidence intervals can be obtained
-
property
timescales
¶ Returns the implied timescale estimates
- Returns
timescales – timescales for all processes and lag times. l is the number of lag times and k is the number of computed timescales.
- Return type
ndarray((l x k), dtype=float)
References
Implied timescales as a lagtime-selection and MSM-validation approach were suggested in 1. Error estimation is done either using moving block bootstrapping 2 or a Bayesian analysis using Metropolis-Hastings Monte Carlo sampling of the posterior. Nonreversible Bayesian sampling is done by independently sampling Dirichtlet distributions of the transition matrix rows. A Monte Carlo method for sampling reversible MSMs was introduced in 3. Here we employ a much more efficient algorithm introduced in 4.
- 1
Swope, W. C. and J. W. Pitera and F. Suits: Describing protein folding kinetics by molecular dynamics simulations: 1. Theory. J. Phys. Chem. B 108: 6571-6581 (2004)
- 2
Kuensch, H. R.: The jackknife and the bootstrap for general stationary observations. Ann. Stat. 17, 1217-1241 (1989)
- 3
Noe, F.: Probability Distributions of Molecular Observables computed from Markov Models. J. Chem. Phys. 128, 244103 (2008)
- 4
Trendelkamp-Schroer, B, H. Wu, F. Paul and F. Noe: Estimation and uncertainty of reversible Markov models. http://arxiv.org/abs/1507.05990
- 5
Nueske, F., Wu, H., Prinz, J.-H., Wehmeyer, C., Clementi, C. and Noe, F.: Markov State Models from short non-Equilibrium Simulations - Analysis and
Correction of Estimation Bias J. Chem. Phys. (submitted) (2017)