GreedyGaussianSegmentation#
- class GreedyGaussianSegmentation(k_max: int = 10, lamb: float = 1.0, max_shuffles: int = 250, verbose: bool = False, random_state: Optional[int] = None)[source]#
Greedy Gaussian Segmentation Estimator.
The method approxmates solutions for the problem of breaking a multivariate time series into segments, where the data in each segment could be modeled as independent samples from a multivariate Gaussian distribution. It uses a dynamic programming search algorithm with a heuristic that allows finding approximate solution in linear time with respect to the data length and always yields locally optimal choice.
Greedy Gaussian Segmentation (GGS) fits a segmented gaussian model (SGM) to the data by computing the approximate solution to the combinatorial problem of finding the approximate covariance-regularized maximum log-likelihood for fixed number of change points and a reagularization strength. It follows an interative procedure where a new breakpoint is added and then adjusting all breakpoints to (approximately) maximize the objective. It is similar to the top-down search used in other change point detection problems.
- Parameters
- k_max: int, default=10
Maximum number of change points to find. The number of segments is thus k+1.
- lamb:float, default=1.0
Regularization parameter lambda (>= 0), which controls the amount of (inverse) covariance regularization, see Eq (1) in [1]. Regularization is introduced to reduce issues for high-dimensional problems. Setting
lamb
to zero will ignore regularization, whereas large values of lambda will favour simpler models.- max_shuffles: int, default=250
Maximum number of shuffles
- verbose: bool, default=False
If
True
verbose output is enabled.- random_state: int or np.random.RandomState, default=None
Either random seed or an instance of
np.random.RandomState
- Attributes
- change_points_: array_like, default=[]
Locations of change points as integer indexes. By convention change points include the identity segmentation, i.e. first and last index + 1 values.
- _intermediate_change_points: List[List[int]], default=[]
Intermediate values of change points for each value of k = 1…k_max
- _intermediate_ll: List[float], default=[]
Intermediate values for log-likelihood for each value of k = 1…k_max
Notes
Based on the work from [1].
source code adapted based on: https://github.com/cvxgrp/GGS
paper available at: https://stanford.edu/~boyd/papers/pdf/ggs.pdf
References
- 1(1,2)
Hallac, D., Nystrup, P. & Boyd, S., “Greedy Gaussian segmentation of multivariate time series.”, Adv Data Anal Classif 13, 727–751 (2019). https://doi.org/10.1007/s11634-018-0335-0
Methods
Check if the estimator has been fitted.
clone
()Obtain a clone of the object with same hyper-parameters.
clone_tags
(estimator[, tag_names])clone/mirror tags from another estimator as dynamic override.
create_test_instance
([parameter_set])Construct Estimator instance if possible.
create_test_instances_and_names
([parameter_set])Create list of all test instances and a list of names for them.
fit
(X[, y])Fit method for compatibility with sklearn-type estimator interface.
fit_predict
(X[, y])Perform segmentation.
get_class_tag
(tag_name[, tag_value_default])Get tag value from estimator class (only class tags).
Get class tags from estimator class and all its parent classes.
Get fitted parameters.
Get parameter defaults for the object.
Get parameter names for the object.
get_params
([deep])Return initialization parameters.
get_tag
(tag_name[, tag_value_default, …])Get tag value from estimator class and dynamic tag overrides.
get_tags
()Get tags from estimator class and dynamic tag overrides.
get_test_params
([parameter_set])Return testing parameter settings for the estimator.
Check if the object is composite.
load_from_path
(serial)Load object from file location.
load_from_serial
(serial)Load object from serialized memory container.
predict
(X[, y])Perform segmentation.
reset
()Reset the object to a clean post-init state.
save
([path])Save serialized self to bytes-like object or to (.zip) file.
set_params
(**parameters)Set the parameters of this object.
set_tags
(**tag_dict)Set dynamic tags to given values.
- fit(X: Union[numpy._typing._array_like._SupportsArray[numpy.dtype], numpy._typing._nested_sequence._NestedSequence[numpy._typing._array_like._SupportsArray[numpy.dtype]], bool, int, float, complex, str, bytes, numpy._typing._nested_sequence._NestedSequence[Union[bool, int, float, complex, str, bytes]]], y: Optional[Union[numpy._typing._array_like._SupportsArray[numpy.dtype], numpy._typing._nested_sequence._NestedSequence[numpy._typing._array_like._SupportsArray[numpy.dtype]], bool, int, float, complex, str, bytes, numpy._typing._nested_sequence._NestedSequence[Union[bool, int, float, complex, str, bytes]]]] = None)[source]#
Fit method for compatibility with sklearn-type estimator interface.
It sets the internal state of the estimator and returns the initialized instance.
- Parameters
- X: array_like
2D array_like representing time series with sequence index along the first dimension and value series as columns.
- y: array_like
Placeholder for compatibility with sklearn-api, not used, default=None.
- predict(X: Union[numpy._typing._array_like._SupportsArray[numpy.dtype], numpy._typing._nested_sequence._NestedSequence[numpy._typing._array_like._SupportsArray[numpy.dtype]], bool, int, float, complex, str, bytes, numpy._typing._nested_sequence._NestedSequence[Union[bool, int, float, complex, str, bytes]]], y: Optional[Union[numpy._typing._array_like._SupportsArray[numpy.dtype], numpy._typing._nested_sequence._NestedSequence[numpy._typing._array_like._SupportsArray[numpy.dtype]], bool, int, float, complex, str, bytes, numpy._typing._nested_sequence._NestedSequence[Union[bool, int, float, complex, str, bytes]]]] = None) Union[numpy._typing._array_like._SupportsArray[numpy.dtype], numpy._typing._nested_sequence._NestedSequence[numpy._typing._array_like._SupportsArray[numpy.dtype]], bool, int, float, complex, str, bytes, numpy._typing._nested_sequence._NestedSequence[Union[bool, int, float, complex, str, bytes]]] [source]#
Perform segmentation.
- Parameters
- X: array_like
2D array_like representing time series with sequence index along the first dimension and value series as columns.
- y: array_like
Placeholder for compatibility with sklearn-api, not used, default=None.
- Returns
- y_predarray_like
1D array with predicted segmentation of the same size as the first dimension of X. The numerical values represent distinct segments labels for each of the data points.
- fit_predict(X: Union[numpy._typing._array_like._SupportsArray[numpy.dtype], numpy._typing._nested_sequence._NestedSequence[numpy._typing._array_like._SupportsArray[numpy.dtype]], bool, int, float, complex, str, bytes, numpy._typing._nested_sequence._NestedSequence[Union[bool, int, float, complex, str, bytes]]], y: Optional[Union[numpy._typing._array_like._SupportsArray[numpy.dtype], numpy._typing._nested_sequence._NestedSequence[numpy._typing._array_like._SupportsArray[numpy.dtype]], bool, int, float, complex, str, bytes, numpy._typing._nested_sequence._NestedSequence[Union[bool, int, float, complex, str, bytes]]]] = None) Union[numpy._typing._array_like._SupportsArray[numpy.dtype], numpy._typing._nested_sequence._NestedSequence[numpy._typing._array_like._SupportsArray[numpy.dtype]], bool, int, float, complex, str, bytes, numpy._typing._nested_sequence._NestedSequence[Union[bool, int, float, complex, str, bytes]]] [source]#
Perform segmentation.
- Parameters
- X: array_like
2D array_like representing time series with sequence index along the first dimension and value series as columns.
- y: array_like
Placeholder for compatibility with sklearn-api, not used, default=None.
- Returns
- y_predarray_like
1D array with predicted segmentation of the same size as the first dimension of X. The numerical values represent distinct segments labels for each of the data points.
- get_params(deep: bool = True) Dict [source]#
Return initialization parameters.
- Parameters
- deep: bool
Dummy argument for compatibility with sklearn-api, not used.
- Returns
- params: dict
Dictionary with the estimator’s initialization parameters, with keys being argument names and values being argument values.
- set_params(**parameters)[source]#
Set the parameters of this object.
- Parameters
- parametersdict
Initialization parameters for th estimator.
- Returns
- selfreference to self (after parameters have been set)
- check_is_fitted()[source]#
Check if the estimator has been fitted.
- Raises
- NotFittedError
If the estimator has not been fitted yet.
- clone()[source]#
Obtain a clone of the object with same hyper-parameters.
A clone is a different object without shared references, in post-init state. This function is equivalent to returning sklearn.clone of self. Equal in value to type(self)(**self.get_params(deep=False)).
- Returns
- instance of type(self), clone of self (see above)
- clone_tags(estimator, tag_names=None)[source]#
clone/mirror tags from another estimator as dynamic override.
- Parameters
- estimatorestimator inheriting from :class:BaseEstimator
- tag_namesstr or list of str, default = None
Names of tags to clone. If None then all tags in estimator are used as tag_names.
- Returns
- Self
Reference to self.
Notes
Changes object state by setting tag values in tag_set from estimator as dynamic tags in self.
- classmethod create_test_instance(parameter_set='default')[source]#
Construct Estimator instance if possible.
- Parameters
- parameter_setstr, default=”default”
Name of the set of test parameters to return, for use in tests. If no special parameters are defined for a value, will return “default” set.
- Returns
- instanceinstance of the class with default parameters
Notes
get_test_params can return dict or list of dict. This function takes first or single dict that get_test_params returns, and constructs the object with that.
- classmethod create_test_instances_and_names(parameter_set='default')[source]#
Create list of all test instances and a list of names for them.
- Parameters
- parameter_setstr, default=”default”
Name of the set of test parameters to return, for use in tests. If no special parameters are defined for a value, will return “default” set.
- Returns
- objslist of instances of cls
i-th instance is cls(**cls.get_test_params()[i])
- nameslist of str, same length as objs
i-th element is name of i-th instance of obj in tests convention is {cls.__name__}-{i} if more than one instance otherwise {cls.__name__}
- parameter_setstr, default=”default”
Name of the set of test parameters to return, for use in tests. If no special parameters are defined for a value, will return “default” set.
- classmethod get_class_tag(tag_name, tag_value_default=None)[source]#
Get tag value from estimator class (only class tags).
- Parameters
- tag_namestr
Name of tag value.
- tag_value_defaultany type
Default/fallback value if tag is not found.
- Returns
- tag_value
Value of the tag_name tag in self. If not found, returns tag_value_default.
- classmethod get_class_tags()[source]#
Get class tags from estimator class and all its parent classes.
- Returns
- collected_tagsdict
Dictionary of tag name : tag value pairs. Collected from _tags class attribute via nested inheritance. NOT overridden by dynamic tags set by set_tags or mirror_tags.
- get_fitted_params()[source]#
Get fitted parameters.
- State required:
Requires state to be “fitted”.
- Returns
- fitted_paramsdict of fitted parameters, keys are str names of parameters
parameters of components are indexed as [componentname]__[paramname]
- classmethod get_param_defaults()[source]#
Get parameter defaults for the object.
- Returns
- default_dict: dict with str keys
keys are all parameters of cls that have a default defined in __init__ values are the defaults, as defined in __init__
- classmethod get_param_names()[source]#
Get parameter names for the object.
- Returns
- param_names: list of str, alphabetically sorted list of parameter names of cls
- get_tag(tag_name, tag_value_default=None, raise_error=True)[source]#
Get tag value from estimator class and dynamic tag overrides.
- Parameters
- tag_namestr
Name of tag to be retrieved
- tag_value_defaultany type, optional; default=None
Default/fallback value if tag is not found
- raise_errorbool
whether a ValueError is raised when the tag is not found
- Returns
- tag_value
Value of the tag_name tag in self. If not found, returns an error if raise_error is True, otherwise it returns tag_value_default.
- Raises
- ValueError if raise_error is True i.e. if tag_name is not in self.get_tags(
- ).keys()
- get_tags()[source]#
Get tags from estimator class and dynamic tag overrides.
- Returns
- collected_tagsdict
Dictionary of tag name : tag value pairs. Collected from _tags class attribute via nested inheritance and then any overrides and new tags from _tags_dynamic object attribute.
- classmethod get_test_params(parameter_set='default')[source]#
Return testing parameter settings for the estimator.
- Parameters
- parameter_setstr, default=”default”
Name of the set of test parameters to return, for use in tests. If no special parameters are defined for a value, will return “default” set.
- Returns
- paramsdict or list of dict, default = {}
Parameters to create testing instances of the class Each dict are parameters to construct an “interesting” test instance, i.e., MyClass(**params) or MyClass(**params[i]) creates a valid test instance. create_test_instance uses the first (or only) dictionary in params
- is_composite()[source]#
Check if the object is composite.
A composite object is an object which contains objects, as parameters. Called on an instance, since this may differ by instance.
- Returns
- composite: bool, whether self contains a parameter which is BaseObject
- classmethod load_from_path(serial)[source]#
Load object from file location.
- Parameters
- serialresult of ZipFile(path).open(“object)
- Returns
- deserialized self resulting in output at path, of cls.save(path)
- classmethod load_from_serial(serial)[source]#
Load object from serialized memory container.
- Parameters
- serial1st element of output of cls.save(None)
- Returns
- deserialized self resulting in output serial, of cls.save(None)
- reset()[source]#
Reset the object to a clean post-init state.
Equivalent to sklearn.clone but overwrites self. After self.reset() call, self is equal in value to type(self)(**self.get_params(deep=False))
Detail behaviour: removes any object attributes, except:
hyper-parameters = arguments of __init__ object attributes containing double-underscores, i.e., the string “__”
runs __init__ with current values of hyper-parameters (result of get_params)
Not affected by the reset are: object attributes containing double-underscores class and object methods, class attributes
- save(path=None)[source]#
Save serialized self to bytes-like object or to (.zip) file.
Behaviour: if path is None, returns an in-memory serialized self if path is a file location, stores self at that location as a zip file
saved files are zip files with following contents: _metadata - contains class of self, i.e., type(self) _obj - serialized self. This class uses the default serialization (pickle).
- Parameters
- pathNone or file location (str or Path)
if None, self is saved to an in-memory object if file location, self is saved to that file location. If:
path=”estimator” then a zip file estimator.zip will be made at cwd. path=”/home/stored/estimator” then a zip file estimator.zip will be stored in /home/stored/.
- Returns
- if path is None - in-memory serialized self
- if path is file location - ZipFile with reference to the file