Mini-batch dictionary learning
Finds a dictionary (a set of atoms) that can best be used to represent data using a sparse code.
Solves the optimization problem::
(U^*,V^* ) = argmin 0.5 || Y - U V ||_2^2 + alpha * || U ||_1 (U,V) with || V_k ||_2 = 1 for all 0 <= k < n_components
Read more in the :ref:`User Guide <DictionaryLearning>`.
Parameters ---------- n_components : int, number of dictionary elements to extract
alpha : float, sparsity controlling parameter
n_iter : int, total number of iterations to perform
fit_algorithm : 'lars', 'cd'
lars: uses the least angle regression method to solve the lasso problem (linear_model.lars_path) cd: uses the coordinate descent method to compute the Lasso solution (linear_model.Lasso). Lars will be faster if the estimated components are sparse.
n_jobs : int or None, optional (default=None) Number of parallel jobs to run. ``None`` means 1 unless in a :obj:`joblib.parallel_backend` context. ``-1`` means using all processors. See :term:`Glossary <n_jobs>` for more details.
batch_size : int, number of samples in each mini-batch
shuffle : bool, whether to shuffle the samples before forming batches
dict_init : array of shape (n_components, n_features), initial value of the dictionary for warm restart scenarios
transform_algorithm : 'lasso_lars', 'lasso_cd', 'lars', 'omp', 'threshold'
Algorithm used to transform the data. lars: uses the least angle regression method (linear_model.lars_path) lasso_lars: uses Lars to compute the Lasso solution lasso_cd: uses the coordinate descent method to compute the Lasso solution (linear_model.Lasso). lasso_lars will be faster if the estimated components are sparse. omp: uses orthogonal matching pursuit to estimate the sparse solution threshold: squashes to zero all coefficients less than alpha from the projection dictionary * X'
transform_n_nonzero_coefs : int, ``0.1 * n_features`` by default Number of nonzero coefficients to target in each column of the solution. This is only used by `algorithm='lars'` and `algorithm='omp'` and is overridden by `alpha` in the `omp` case.
transform_alpha : float, 1. by default If `algorithm='lasso_lars'` or `algorithm='lasso_cd'`, `alpha` is the penalty applied to the L1 norm. If `algorithm='threshold'`, `alpha` is the absolute value of the threshold below which coefficients will be squashed to zero. If `algorithm='omp'`, `alpha` is the tolerance parameter: the value of the reconstruction error targeted. In this case, it overrides `n_nonzero_coefs`.
verbose : bool, optional (default: False) To control the verbosity of the procedure.
split_sign : bool, False by default Whether to split the sparse feature vector into the concatenation of its negative part and its positive part. This can improve the performance of downstream classifiers.
random_state : int, RandomState instance or None, optional (default=None) Used for initializing the dictionary when ``dict_init`` is not specified, randomly shuffling the data when ``shuffle`` is set to ``True``, and updating the dictionary. Pass an int for reproducible results across multiple function calls. See :term:`Glossary <random_state>`.
positive_code : bool Whether to enforce positivity when finding the code.
.. versionadded:: 0.20
positive_dict : bool Whether to enforce positivity when finding the dictionary.
.. versionadded:: 0.20
transform_max_iter : int, optional (default=1000) Maximum number of iterations to perform if `algorithm='lasso_cd'` or `lasso_lars`.
.. versionadded:: 0.22
Attributes ---------- components_ : array, n_components, n_features
components extracted from the data
inner_stats_ : tuple of (A, B) ndarrays Internal sufficient statistics that are kept by the algorithm. Keeping them is useful in online settings, to avoid losing the history of the evolution, but they shouldn't have any use for the end user. A (n_components, n_components) is the dictionary covariance matrix. B (n_features, n_components) is the data approximation matrix
n_iter_ : int Number of iterations run.
iter_offset_ : int The number of iteration on data batches that has been performed before.
random_state_ : RandomState RandomState instance that is generated either from a seed, the random number generattor or by `np.random`.
Notes ----- **References:**
J. Mairal, F. Bach, J. Ponce, G. Sapiro, 2009: Online dictionary learning for sparse coding (https://www.di.ens.fr/sierra/pdfs/icml09.pdf)
See also -------- SparseCoder DictionaryLearning SparsePCA MiniBatchSparsePCA